Wait and poll instructions for monitoring a plurality of addresses

ABSTRACT

A processor core includes a decode circuit to decode an instruction. The processor core further includes a monitor circuit, where the monitor circuit includes a data structure to store a plurality of entries for addresses that are being monitored by the monitor circuit and a triggered queue to store a plurality of addresses for which a triggering event occurred. The processor core further includes an execution circuit to execute the decoded instruction to dequeue an address from the triggered queue and return the dequeued address in response to a determination that the triggered queue is not empty.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/394,271,filed Dec. 29, 2016, which is hereby incorporated by reference.

TECHNICAL FIELD

Embodiments of the invention relate to the field of computer instructionset architecture; and more specifically, to instructions for monitoringmultiple addresses.

BACKGROUND

Many computing applications can benefit from the use of fine-grainedparallelism to reduce load imbalance and to allow for more paralleloperations. With fine-grained parallelism, an application is dividedinto a large number of small tasks and these tasks are assigned acrossmultiple processors. However, the overhead of scheduling tasks andswitching between tasks is typically too high for existing hardware toeffectively exploit fine-grained parallelism.

One approach for implementing fine-grained parallelism is an approachthat is implemented solely in software. This approach typically requiresan active polling mechanism that periodically checks whether there isdata that is ready for consumption. However, this approach typicallyincurs high overhead. Another approach for implementing fine-grainedparallelism is to implement a full tasking system in hardware. However,this approach is inflexible with regard to usage pattern and the numberof tasks it can support.

In modern high-performance processors, fine-grained parallelism can beachieved by synchronizing threads via shared memory. For example, athread may register an address to be monitored and enter an optimizedstate (e.g., low-power mode) until data is written to that address. Forthis purpose, a processor's instruction set architecture may includeinstructions to monitor a specified address for write-to-memoryactivities. For example, a processor's instruction set architecture mayinclude a MONITOR instruction and an MWAIT instruction. The MONITORinstruction allows software to specify an address range to monitor. TheMWAIT instruction allows software to instruct the logical processor toenter an optimized state (which may vary depending on implementations)until a write operation to the address range specified by the MONITORinstruction occurs. The MONITOR/MWAIT instructions can thus be used tomonitor a single address range.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 is a block diagram illustrating a processor for executinginstructions to monitor multiple addresses, according to someembodiments.

FIG. 2A is a block diagram illustrating a dual-core processor that isconfigured to monitor multiple addresses, according to some embodiments.

FIG. 2B is a block diagram illustrating a dual-core processor that isconfigured to monitor multiple addresses that implements a shared L2cache, according to some embodiments.

FIG. 3 is a block diagram illustrating a monitor unit, according to someembodiments.

FIG. 4A-4E are diagrams illustrating exemplary operations of theNMONITOR instruction and NWAIT/NPOLL instruction, according to someembodiments.

FIG. 5 is a flow diagram of a process performed by a core to execute anNMONITOR instruction, according to some embodiments.

FIG. 6 is a flow diagram of a process performed by a monitor unit of acore to monitor addresses, according to some embodiments.

FIG. 7 is a flow diagram of a process performed by a core to execute anNWAIT or NPOLL instruction, according to some embodiments.

FIG. 8 is a flow diagram of a process performed by a core to process anNMONITOR instruction, according to some embodiments.

FIG. 9 is a flow diagram of a process performed by a processor core toprocess an NWAIT instruction, according to some embodiments.

FIG. 10 is a flow diagram of a process performed by a core to process anNPOLL instruction, according to some embodiments.

FIG. 11 is a flow diagram of a process performed by a core to process anNMONITOR instruction followed by an NWAIT instruction, according to someembodiments.

FIG. 12 is a flow diagram of a process performed by a core to process anNMONITOR instruction followed by an NPOLL instruction.

FIGS. 13A-13B are block diagrams illustrating a generic vector friendlyinstruction format and instruction templates thereof according toembodiments of the invention;

FIG. 13A is a block diagram illustrating a generic vector friendlyinstruction format and class A instruction templates thereof accordingto embodiments of the invention;

FIG. 13B is a block diagram illustrating the generic vector friendlyinstruction format and class B instruction templates thereof accordingto embodiments of the invention;

FIG. 14A is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to embodiments of the invention;

FIG. 14B is a block diagram illustrating the fields of the specificvector friendly instruction format 1400 that make up the full opcodefield 1374 according to one embodiment of the invention;

FIG. 14C is a block diagram illustrating the fields of the specificvector friendly instruction format 1400 that make up the register indexfield 1344 according to one embodiment of the invention;

FIG. 14D is a block diagram illustrating the fields of the specificvector friendly instruction format 1400 that make up the augmentationoperation field 1350 according to one embodiment of the invention;

FIG. 15 is a block diagram of a register architecture 1500 according toone embodiment of the invention;

FIG. 16A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention;

FIG. 16B is a block diagram illustrating both an exemplary embodiment ofan in-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention;

FIGS. 17A-B illustrate a block diagram of a more specific exemplaryin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip;

FIG. 17A is a block diagram of a single processor core, along with itsconnection to the on-die interconnect network 1702 and with its localsubset of the Level 2 (L2) cache 1704, according to embodiments of theinvention;

FIG. 17B is an expanded view of part of the processor core in FIG. 17Aaccording to embodiments of the invention;

FIG. 18 is a block diagram of a processor 1800 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention;

FIGS. 19-22 are block diagrams of exemplary computer architectures;

FIG. 19 shown a block diagram of a system in accordance with oneembodiment of the present invention;

FIG. 20 is a block diagram of a first more specific exemplary system inaccordance with an embodiment of the present invention;

FIG. 21 is a block diagram of a second more specific exemplary system inaccordance with an embodiment of the present invention;

FIG. 22 is a block diagram of a SoC in accordance with an embodiment ofthe present invention; and

FIG. 23 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the disclosure may bepracticed without these specific details. In other instances, well-knowncircuits, structures and techniques have not been shown in detail to notobscure the understanding of this description.

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment need not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

A processor's instruction set architecture may include instructions tomonitor a specified address for write-to-memory activities. For example,a processor's instruction set architecture may include a MONITORinstruction and an MWAIT instruction. The MONITOR instruction allowssoftware to specify an address range to monitor. The MWAIT instructionallows software to instruct the logical processor to enter an optimizedstate (which may vary depending on implementations) until a writeoperation to the address range specified by the MONITOR instructionoccurs. The MONITOR/MWAIT instructions can be used to monitor a singleaddress range. However, it may be beneficial to be able to monitormultiple non-contiguous addresses instead of monitoring just a singleaddress or a single address range. This would allow software to beasynchronously notified regarding write operations to multiple(non-contiguous) addresses and not just a single address or a singlerange of addresses. This way, rather than waiting for a singlepredefined event, software can register multiple events that it isinterested in, where each event corresponds to an address that will bewritten by another actor. Software can then be asynchronously notifiedwhen any of the events occur and act upon that event.

Embodiments disclosed herein provide a monitoring infrastructure thatallows for monitoring multiple addresses. A new instruction referred toherein as “NMONITOR” is introduced that allows software to specify theaddresses to be monitored. Also, a new instruction referred to herein as“NWAIT” is introduced that allows software to instruct the logicalprocessor to enter an optimized state (e.g., low-power mode) until awrite operation (or other triggering event) to one of the addressesbeing monitored (as specified by the NMONITOR instruction) occurs. TheNWAIT instruction may return the address for which the write operationoccurred to software. Also, a new instruction referred to herein as“NPOLL” is introduced that allows software to determine whether a writeoperation (or other triggering event) to one of the addresses beingmonitored (e.g., as specified by the NMONITOR instruction) has occurred.The NPOLL instruction is a non-blocking variant of the NWAIT instructionthat may immediately return either an address for which a writeoperation occurred (e.g., if a write operation to one of the addressesbeing monitored has occurred) or immediately return an indication that atriggering event for an address being monitored has not occurred.

Embodiments disclosed herein may be advantageous for several use cases.In high-throughput network communications scenarios, the networkinterface writes incoming data packets directly to a buffer inuser-space visible memory. Typically, an application dispatch threadpolls on “ready” or “head” address to which the network interfacewrites. The dispatch thread may use the NMONITOR instruction to registermultiple head addresses (corresponding to multiple message queues) formonitoring. The dispatch thread may use the NWAIT instruction to go tosleep until one of the buffers has new data for consumption. The returnvalue of the NWAIT instruction allows the dispatch thread to know whichof the buffers has received new data. When compared with active pollingtechniques, the NWAIT instruction may utilize the processor core's sleepstate to reduce power consumption. Also, the NWAIT instructionimmediately returns the “ready” address, which frees the software fromthe overhead involved with searching for a “ready” state over a set ofaddresses on every poll cycle. This contributes to the reduced powerconsumption and also improves the user-thread response time.

Fine-grained parallelism has become a staple of high-performancemultithreaded programming and event-driven interactive applications, butits usefulness is limited to problems that unify control and datarelationships. Tasking models have been proposed that add datadependencies to tasks. However, tracking these data dependenciesintroduces the scheduling overhead of searching for ready tasks, whichlimits its usefulness to long-running tasks. Nevertheless, severalhigh-level programming languages are increasingly adopting data-drivenasynchronous programming styles, so as to improve the latency orresponsiveness of applications. For example, this data-drivenasynchronous programming style can be achieved using programminglanguage constructs such as futures/promises or async/await. With theNMONITOR/NWAIT instructions, data-driven task schedulers can avoid theoverhead of searching for ready tasks, which makes them suitable forimplementing fine-grained parallelism in high-performance computingenvironments as well as accelerating existing reactive programmingconstructs (e.g., futures/promises and async/await).

FIG. 1 is a block diagram illustrating a processor for executinginstructions to monitor multiple addresses, according to someembodiments. The processor 100 includes instruction storage 102, fetchcircuit 103, decode circuit 104, execution circuit 106, monitor unit 120(which may also be referred to as a monitor circuit), registers 108,memory 110, and retire or commit circuit 112. An instruction is fetchedby fetch circuit 103 from instruction storage 102. In one embodiment,the instruction storage 102 comprises any one or more of a cache memory,an on-chip memory, a memory on the same die as the processor 100, aninstruction register, a general register, and system memory. Decodecircuit 104 decodes the fetched instruction. In one embodiment, theinstruction is an NMONITOR instruction or an NWAIT/NPOLL instruction.The decoded instruction is executed by execution circuit 106. Executioncircuit 106 is configured to read data from and write data to registers108 and memory 110. In one embodiment, registers 108 comprise any one ormore of a data register, an instruction register, a general register,and an on-chip memory. In one embodiment, memory 110 comprises any oneor more of an on-chip memory, a memory on the same die as the processor100, a memory in the same package as the processor 100, a cache memory,and system memory. Execution circuit 106 is further configured tointeract with monitor unit 120 to support the monitoring of multipleaddresses. An exemplary embodiment of monitoring unit 120 is illustratedand described with reference to FIG. 3. Retire or commit circuit 112ensures that execution results are written to or have been written totheir destinations, and frees up or releases resources for later use.For this purpose, retire or commit circuit 112 is configured to readdata from and write data to register 108 and memory 110.

FIG. 2A is a block diagram illustrating a dual-core processor that isconfigured to monitor multiple addresses, according to some embodiments.The processor 100 includes two processor cores (210A and 210B). Eachprocessor core 210 includes a monitor unit 120. For example, processorcore 210A includes monitor unit 120A and processor core 210B includesmonitor unit 120B. Each processor core also includes a private L2 cache230. For example, processor core 210A includes private L2 cache 230A andprocessor core 210B includes private L2 cache 230B. The processor 100 isconnected to a chipset 240 and may be employed to execute programinstructions. In one embodiment, a given “physical” processor core 210implements one or more “logical” cores. For example, under the Intel®Hyperthreading™ architecture, each physical core 210 implements twological cores. When a processor core 210 implements one or more logicalprocessor cores, a monitor unit 120 may be provisioned for each logicalprocessor core. Throughout the description, physical processor cores 210and logical processor cores may be generally referred to as “cores” or“processor cores”. FIG. 2B is a block diagram illustrating a dual-coreprocessor similar to that illustrated in FIG. 2A, except that theprocessor 100 implements a shared L2 cache 230.As shown in FIG. 2A,processor core 210A and processor core 210B share L2 cache 230.AlthoughFIG. 2A and FIG. 2B illustrate a dual-core processor, it should beunderstood that the techniques described herein are equally applicablein contexts where a processor 100 has more than two processor cores 210.

FIG. 3 is a block diagram illustrating a monitor unit, according to someembodiments. The monitor unit 120 includes an armed table 310, atriggered queue 320, and an overflow bit 330. In one embodiment, eachcore of a multi-core processor 100 includes a monitoring unit 120. Inone embodiment, when simultaneous multithreading (SMT) techniques (e.g.,Intel® Hyperthreading™) are employed, each thread or hardware contexthas a dedicated monitor unit 120. The armed table 310 maintains theaddresses that are registered to be monitored by the monitor unit 120.In one embodiment, an entry for each address being monitored by themonitor unit 120 is stored in the armed table 310. As shown in the blockdiagram, the armed table 310 can store up to five entries (since thearmed table 310 is provisioned with five rows). It should be understood,however, that in other embodiments, the armed table 310 is capable ofstoring more or less than five entries. In one embodiment, the armedtable 310 includes a free column, a physical address column, and alogical address column. The free column indicates whether an entry isfree. The physical address column indicates the physical address of anaddress that is being monitored. The logical address column indicatesthe logical address of an address that is being monitored. The triggeredqueue 320 maintains the logical addresses of the addresses for which atriggering event has occurred. As shown in the block diagram, thetriggered queue 320 can store up to five logical addresses (fiveelements). It should be understood, however, that in other embodiments,the triggered queue 320 is capable of storing more or less than fivelogical addresses. The overflow bit 330 indicates whether the triggeredqueue 320 has overflowed.

An NMONITOR instruction may take the address that is to be monitored asan argument (e.g., with cache line granularity). When the NMONITORinstruction is called with a specified address to be monitored, the corethat executes the instruction adds an entry for the specified address inits monitor unit 120 (e.g., in the armed table 310). The entry includesthe physical address corresponding to the specified address in thephysical address column and the logical address corresponding to thespecified address (which is the specified address itself when thespecified address is a logical address) in the logical address column.In one embodiment, an address translation logic is employed to determinethe physical address corresponding to the specified address. The entryis marked as not being free (in the free column) to indicate that theentry is valid/occupied. The core also ensures that the cache linecorresponding to the specified address is in (S)hared state in thecore's cache (e.g., L2 cache 230). In one embodiment, this is achievedusing a cache coherence protocol. For example, assuming a MESI-type(Modified-Exclusive-Shared-Invalid) protocol is used for cachecoherency, a cache line in (M)odified state or (E)xclusive state istransitioned to (S)hared state, and an (I)nvalid cache line is loadedinto the cache in (S)hared state. This ensures that when another coreattempts to write to this cache line, a state transition will occur.This also allows multiple cores to monitor the address because multiplecopies of a cache line in (S)hared state are allowed. In a MESI-typeprotocol, the (S)hared state indicates that the cache line may be storedin other caches and is clean (it matches main memory). At this stage,the monitor unit 120 is configured to monitor the specified address.

In one embodiment, an extra bit is added to each cache line (e.g., inthe core's L2 cache 230) to indicate whether the cache line correspondsto an address that is being monitored. In one embodiment, since thecache line corresponding to an address that is being monitored isguaranteed to be in a shared state ((S)hared state in MESI-typeprotocol), the indication can be encoded implicitly using an unusedcombination of existing state bits, and thus not take up any extrastorage space.

The NMONITOR instruction may be called multiple times, each time with adifferent address, to register multiple addresses for monitoring(simultaneously). Each call to the NMONITOR instruction adds an entryfor an address to be monitored to the armed table 310. If an entry forthe address is already in the armed table 310, then the NMONITORinstruction returns a MONITOR-EXISTS fault code to indicate that theaddress is already being monitored. If a free entry is not available inthe armed table 310 (the armed table 310 is full), then the NMONITORinstruction returns a MONITOR-FULL fault code to indicate that theaddress cannot be monitored. Based on this fault code, software maydecide to fall back to an alternative way to detect write operations tothe address (e.g., involving hierarchical monitoring structure orpolling).

When a triggering event for an address occurs, a trigger event messageconveying the physical address of the address is sent to the core'smonitor unit 120. The triggering event for an address that causes atrigger event message to be sent to the core's monitor unit 120 may be astate transition of the cache line corresponding to the address from(S)hared state to (I)nvalid state (e.g., when another core writes to thecache line), a state transition from (S)hared state to (M)odified state(e.g., when a core holding an active monitor writes to the cache line),or a voluntary eviction of the cache line from the cache 230.If multiplecores share the cache (or when each core has multiple hardwarecontexts), each of the respective monitoring units 120 is sent a triggerevent message conveying the physical address of the address for whichthe triggering event occurred. In one embodiment, the trigger eventmessage is received based on snooping a bus that carries informationthat is used to maintain the coherency status of cache lines.

When the monitor unit 120 receives a trigger event message, the monitorunit 120 checks whether an entry matching the physical address conveyedby the trigger event message exists in the armed table 310 (i.e., avalid (non-free) entry that has a value in the physical address columnthat matches the physical address conveyed by the trigger eventmessage). If no such entry is found in the armed table 310, then this isconsidered a spurious triggering event (e.g., caused by another core orthread initiating the monitor) that is silently ignored. If a matchingentry is found in the armed table 310, then the entry is freed (e.g., bysetting the free column to indicate that the entry is free) and thelogical address of the entry is enqueued into the triggered queue 320.In one embodiment, if the logical address of the entry cannot beenqueued into the triggered queue 320 due to the triggered queue 320being full, then the monitor unit 120 sets the overflow bit 330 toindicate that the triggered queue 320 has overflowed.

When the NWAIT or NPOLL instruction is called, unless there is an errorcondition (examples of which are described further below), the NWAIT orNPOLL instruction returns the logical address at the head of thetriggered queue 320 (assuming the triggered queue 320 is not empty) andthis logical address is dequeued from the triggered queue 320. If theoverflow bit 330 is set to indicate that the triggered queue 320 hasoverflowed, then the NWAIT or NPOLL instruction returns aTRIGGERED-OVERFLOW fault code to indicate that the triggered queue 320has overflowed and the overflow bit is reset. Subsequent calls to theNWAIT or NPOLL instruction will see that the overflow bit is reset andwill be able to return any remaining logical addresses in the triggeredqueue 320.

With the NWAIT instruction, if the triggered queue 320 is empty (it hasno elements), then the core (e.g., a physical core or a logical core)may enter an optimized state (which may vary depending onimplementations) until a write operation (or other triggering event) toone of the addresses being monitored by the monitor unit 120 occurs.When a write operation (or other triggering event) to one of theaddresses being monitored by the monitor unit 120 occurs, the core exitsthe optimized state and the NWAIT instruction returns the address forwhich the write operation (or other triggering event) occurred. However,with the NPOLL instruction, if the triggered queue 320 is empty, aNO-TRIGGERED fault code is immediately returned to indicate that atriggering event for the addresses being monitored has not occurred.

In one embodiment, the return value of the NWAIT or NPOLL instruction isstored in a single register (e.g., a destination register). In oneembodiment, for valid triggering events, the return value for the NWAITor NPOLL instruction is a cache line base address, and thus its lowerbits (corresponding to a cache line offset) are zero. In one embodiment,for fault conditions, the lower bits indicate a (non-zero) fault code.If both the armed table 310 and the triggered queue 320 are empty, thenno future triggering events can be expected and thus the NWAIT or NPOLLinstruction returns a NO-ARMED fault code to indicate as such.

Whenever a context switch occurs on the core or the logical address tophysical address mapping changes for some reason, all outstandingmonitors are cleared. This may be achieved by clearing the entries inthe armed table 310, clearing the elements in the triggered queue 320,and resetting the overflow bit 330. Software may detect when thishappens because a call to NWAIT or NPOLL will return a NO-ARMED faultcode, indicating that a context switch or other event occurred thatcleared all outstanding monitors. Software may then re-register theaddresses that it is still interested in monitoring (e.g., using theNMONITOR instruction), and proceed as usual.

FIG. 4A is a diagram illustrating exemplary operations of the NMONITORinstruction and NWAIT instruction, according to some embodiments. Inthis example, software calls the NMONITOR instruction for addresses1_addr_a, 1_addr_b, and 1_addr_c, respectively. These instructions causethe core (that executes the NMONITOR instructions) to add an entry foreach of the addresses to the armed table 310 of its monitoring unit 120to monitor these addresses. Each entry includes the logical addresscorresponding to the address (the logical address is the same as thespecified address in this example) and the physical addresscorresponding to the address (e.g., p_addr_a is the physical addresscorresponding to p_addr_a p_addr_b is the physical address correspondingto 1_addr_b and so forth). Also, the core ensures that the coherencystatus of the cache lines corresponding to 1_addr_a, 1_addr_b, and1_addr_c are in a shared state (e.g., using a cache coherence protocol).Software then calls the NWAIT instruction before any triggering eventsfor the addresses being monitored occurs (and thus the triggered queue320 is empty). Since the triggered queue 320 is empty, the core thatexecutes the NWAIT instruction enters an optimized state.

Subsequently, as shown in FIG. 4B, data stored at p_addr_b is modified.This is considered a triggering event for 1_addr_b. The monitor unit 120is notified of this triggering event. In response, the monitor unit 120enqueues 1_addr_b into the triggered queue 320 and marks the entry for1_addr_b in the armed table 310 as being free. In one embodiment, themonitor unit 120 sends a signal to the core to exit the optimized state.The core then exits the optimized state, dequeues 1_addr_b from thetriggered queue 320, and provides 1_addr_b as the return value for thepreviously called NWAIT instruction.

Subsequently, as shown in FIG. 4C, data stored at p_addr_a is modifiedand data stored at p_addr_c is evicted. These are considered triggeringevents for 1_addr_a and 1_addr_c, respectively. The monitor unit 120 isnotified of these triggering events. In response, the monitor unit 120enqueues 1_addr_a and 1_addr_c into the triggered queue 320 and marksthe entries for 1_addr_a and 1_addr_c in the armed table 310 as beingfree.

As shown in FIG. 4D, software then calls the NWAIT instruction. Sincethe triggered queue 320 is not empty, the core provides the logicaladdress at the head of the triggered queue 320 as the return value forthe NWAIT instruction, which is 1_addr_a in this example. The core thendequeues 1_addr_a from the triggered queue 320. Once 1_addr_a isdequeued, 1_addr_c is at the head of the triggered queue 320.Subsequently, software calls the NPOLL instruction. Since the triggeredqueue 320 is not empty, the core provides the logical address at thehead of the triggered queue 320 as the return value for the NPOLLinstruction, which in this example is now 1_addr_c. The core thendequeues 1_addr_c from the triggered queue 320 (and the triggered queue320 is now empty).

As shown in FIG. 4E, software calls the NMONITOR instruction for address1_addr_d. This instruction causes the core (that executes the NMONIOTRinstruction) to add an entry for 1_addr_d to the armed table 310. Also,the core ensures that the coherency status of the cache linecorresponding to 1_addr_d is in a shared state (e.g., using a cachecoherence protocol). Software then calls the NPOLL instruction (before atriggering event for 1_addr_d occurs). Since the triggered queue 320 isempty, the core provides a NO-TRIGGERED fault code as the return valuefor the NPOLL instruction.

FIG. 5 is a flow diagram of a process performed by a core to execute anNMONITOR instruction, according to some embodiments. The operations inthe flow diagrams will be described with reference to the exemplaryembodiments of the other figures. However, it should be understood thatthe operations of the flow diagrams can be performed by embodimentsother than those discussed with reference to the other figures, and theembodiments discussed with reference to these other figures can performoperations different than those discussed with reference to the flowdiagrams.

In one embodiment, the process is initiated when the core receives anNMONITOR instruction that specifies an address to be monitored (block505 ). The core determines whether an entry for the address alreadyexists in the armed table 310 (decision block 510). If an entry for theaddress already exists in the armed table 310, then the core returns anindication that the address is already being monitored (e.g.,MONITOR-EXISTS fault code). However, if an entry for the address doesnot already exist in the armed table 310, then the core determineswhether a free entry is available in the armed table 310 (decision block520). If a free entry is not available in the armed table 310, then thecore returns an indication that the armed table 310 is full (e.g.,MONITOR-FULL fault code). However, if the core determines that there isa free entry available in the armed table 310, then the core adds anentry for the address in the armed table 310 (block 530). In oneembodiment, this involves marking the entry as no longer being free. Thecore then ensures that the coherency status of the cache linecorresponding to the address is in a shared state (block 535). The corethen returns an indication that the address is being monitored (e.g.,return value of 0) (block 540).

FIG. 6 is a flow diagram of a process performed by a monitor unit of acore to monitor addresses, according to some embodiments. In oneembodiment, the process is performed by a monitor unit 120 (or monitorcircuit) of a core. In one embodiment, the process is initiated when themonitor unit 120 receives a trigger event message for an address (block605). The monitor unit 120 determines whether an entry for the addressexists in the armed table 310 (e.g., by comparing the physical addressconveyed by the trigger event message to the physical address indicatedby entries in the armed table 310) (decision block 610). If an entry forthe address does not exist in the armed table 310, then the monitor unit120 ignores the trigger event message (at least for monitoring purposes)(block 615). However, if an entry for the address exists in the armedtable 310, then the monitor unit 120 frees that entry (block 620). Themonitor unit 120 then determines whether the triggered queue 320 is full(decision block 625). If the triggered queue 320 is full, then themonitor unit 120 sets the overflow indicator of the triggered queue 320(block 635). However, if the triggered queue 320 is not full, then themonitor unit 120 enqueues the address (e.g., logical address) into thetriggered queue 320 (block 630).

FIG. 7 is a flow diagram of a process performed by a core to execute anNWAIT or NPOLL instruction, according to some embodiments. In oneembodiment, the process is initiated when the core receives an NWAIT orNPOLL instruction. The core determines whether the overflow indicator ofthe triggered queue 320 is set (decision block 710). If the overflowindicator is set, then the core resets the overflow indicator andreturns an indication that the triggered queue 320 has overflowed (e.g.,TRIGGERED-OVERFLOW fault code). However, if the overflow indicator isnot set, then the core determines whether the triggered queue 320 isempty (decision block 725). If the triggered queue 320 is not empty,then the core dequeues an address from the triggered queue 320 (block730) and returns this dequeued address (block 735). However, if thetriggered queue 320 is empty, then the core determines whether the armedtable 310 is empty (decision block 740). If the armed table 310 isempty, then the core returns an indication that no addresses are beingmonitored (e.g., NO-ARMED fault code). In the case of the WAITinstruction, if the armed table 310 is not empty, the core may enter anoptimized state (e.g., a power-saving mode) until a triggering event foran address being monitored occurs (block 750). Once a triggering eventfor an address being monitored occurs, the core may exit the optimizedstate. At this stage, the address for which the triggering eventoccurred should be at the head of the triggered queue 320. The coredequeues this address from the triggered queue 320 and returns thedequeued address (blocks 730 and 735). Returning to decision block 740,in the case of the NPOLL instruction, if the armed table 310 is notempty, the core immediately (without entering into an optimized state)returns an indication that a triggering event for an address beingmonitored has not been detected (e.g., NO-TRIGGERED fault code) (block755).

FIG. 8 is a flow diagram of a process performed by a core to process anNMONITOR instruction, according to some embodiments. At block 805, aninstruction is fetched. For example, an NMONITOR instruction is fetched,where the NMONITOR instruction specifies an address to be monitored. Inone embodiment, the instruction is fetched from an instruction storage102. At block 810, the fetched instruction is decoded by a decodecircuit 104. For example, the fetched NMONITOR instruction is decoded.At block 815, the decoded instruction is executed by an executioncircuit 106. For the NMONITOR instruction, at block 820, the executionretrieves the specified address to be monitored (e.g., as specified bythe NMONITOR instruction). At block 825, the execution further adds anentry for the specified address to be monitored into a data structure(e.g., armed table 310) of a monitor circuit 120 and ensures (using acache coherence protocol) that a coherency status of a cache linecorresponding to the specified address to be monitored is in a sharedstate, where the monitor circuit 120 is to enqueue the specified addressto be monitored into a triggered queue 320 of the monitor circuit 120 inresponse to a determination that a triggering event for the specifiedaddress to be monitored occurred. In one embodiment, the execution is toreturn an indication that the specified address to be monitored isalready being monitored by the monitor circuit 120 (e.g., MONITOR-EXISTSfault code) in response to a determination that the entry for thespecified address to be monitored exists in the data structure. In oneembodiment, the execution is to return an indication that the datastructure is full (e.g., MONITOR-FULL fault code) in response to adetermination that there is no free entry available in the datastructure. In one embodiment, the monitor circuit 120 is to free theentry for the specified address to be monitored in response to thedetermination that the triggering event for the specified address to bemonitored occurred. In one embodiment, the monitor circuit 120 includesan overflow indicator (e.g., overflow bit 330), and the monitor circuit120 is to set the overflow indicator in response to a determination thatthe triggered queue 320 has overflowed. In one embodiment, the monitorcircuit 120 is to determine that a triggering event for the specifiedaddress being monitored occurred based on a determination that that thecoherency status of the cache line corresponding to the specifiedaddress to be monitored has changed (e.g., based on receiving a triggerevent message). In one embodiment, the entry for the specified addressto be monitored includes an indication of a logical addresscorresponding to the specified address to be monitored and an indicationof a physical address corresponding to the specified address to bemonitored (e.g., as shown in FIG. 4A). In one embodiment, at block 830,the instruction is committed or retired.

FIG. 9 is a flow diagram of a process performed by a core to process anNWAIT instruction, according to some embodiments. At block 905, aninstruction is fetched. For example, an NWAIT instruction is fetched. Inone embodiment, the instruction is fetched from an instruction storage102. At block 910, the fetched instruction is decoded by a decodecircuit 104. For example, the fetched NWAIT instruction is decoded. Atblock 915, the decoded instruction is executed by an execution circuit106. For the NWAIT instruction, at block 920, the execution dequeues anaddress from a triggered queue 320 of a monitor circuit 120 and returnsthe dequeued address in response to a determination that the triggeredqueue 320 is not empty, causes the core to enter an optimized state inresponse to a determination that the triggered queue 320 is empty, andcauses the core to exit the optimized state in response to adetermination that a triggering event for an address being monitored bythe monitor circuit 120 occurred. In one embodiment, the monitor circuit120 includes an overflow indicator (e.g., overflow bit 330), and theexecution is to return an indication that the triggered queue 320 hasoverflowed (e.g., TRIGGERED-OVERVLOW fault code) in response to adetermination that the overflow indicator is set and reset the overflowindicator. In one embodiment, the execution is to return an indicationthat no addresses are being monitored by the monitor circuit 120 (e.g.,NO-ARMED fault code) in response to a determination that the triggeredqueue 320 is empty and the data structure (e.g., armed table 310) isempty. In one embodiment, the execution is to determine that the datastructure is empty based on a determination that a content of the datastructure indicates that no addresses are being monitored by the monitorcircuit 120. In one embodiment, the execution is to store the dequeuedaddress in a destination register. In one embodiment, at block 930, theinstruction is committed or retired.

FIG. 10 is a flow diagram of a process performed by a core to process anNPOLL instruction, according to some embodiments. At block 1005, aninstruction is fetched. For example, an NPOLL instruction is fetched. Inone embodiment, the instruction is fetched from an instruction storage102. At block 1010, the fetched instruction is decoded by a decodecircuit 104. For example, the fetched NPOLL instruction is decoded. Atblock 1015, the decoded instruction is executed by an execution circuit106. For the NPOLL instruction, at block 920, the execution dequeues anaddress from a triggered queue 320 of a monitor circuit 120 and returnsthe dequeued address in response to a determination that the triggeredqueue 320 is not empty and returns an indication that a triggering eventfor an address being monitored by the monitor circuit 120 has notoccurred (e.g., NO-TRIGGERED fault code) in response to a determinationthat the triggered queue 320 is empty. In one embodiment, the monitorcircuit 120 includes an overflow indicator (e.g., overflow bit 330), andthe execution is to return an indication that the triggered queue 320has overflowed in response to a determination that the overflowindicator is set and reset the overflow indicator. In one embodiment,the execution is to return an indication that no addresses are beingmonitored by the monitor circuit 120 in response to a determination thatthe triggered queue 320 is empty and the data structure is empty. In oneembodiment, the execution is to determine that the data structure isempty based on a determination that a content of the data structureindicates that no addresses are being monitored by the monitor circuit120. In one embodiment, the execution is to store the dequeued addressin a destination register. In one embodiment, at block 1030, theinstruction is committed or retired.

FIG. 11 is a flow diagram of a process performed by a core to process anNMONITOR instruction followed by an WAIT instruction, according to someembodiments. At block 1105, an NMONITOR instruction is fetched, wherethe NMONITOR instruction specifies an address to be monitored. In oneembodiment, the NMONITOR instruction is fetched from an instructionstorage 102. At block 1110, the fetched NMONITOR instruction is decodedby a decode circuit 104. At block 1115, the address specified by theNMONITOR instruction is retrieved. At block 1120, the NMONITORinstruction is executed by an execution circuit 106 to add an entry forthe specified address to be monitored into a data structure (e.g., armedtable 310) of a monitor circuit 120 and ensure (using a cache coherenceprotocol) that a coherency status of a cache line corresponding to thespecified address to be monitored is in a shared state, where themonitor circuit 120 is to enqueue the specified address to be monitoredinto a triggered queue 320 of the monitor circuit 120 in response to adetermination that a triggering event for the specified address to bemonitored occurred. In one embodiment, at block 1125, the NMONITORinstruction is committed or retired.

The NMONITOR instruction thus registers a specified address to bemonitored by the monitor circuit 120. The NMONITOR instruction may becalled multiple times, each time with a different address, to registermultiple addresses for monitoring. The number of addresses that can bemonitored simultaneously is only limited by the size of the datastructure (e.g., armed table 310).

At block 1130, an NWAIT instruction is fetched. In one embodiment, theNWAIT instruction is fetched from an instruction storage 102. At block1135, the fetched NWAIT instruction is decoded by a decode circuit 104.At block 1140, the NWAIT instruction is executed by an execution circuit160 to dequeue an address from a triggered queue 320 of a monitorcircuit 120 and return the dequeued address in response to adetermination that the triggered queue 320 is not empty, cause the coreto enter an optimized state in response to a determination that thetriggered queue 320 is empty, and cause the core to exit the optimizedstate in response to a determination that a triggering event for anaddress being monitored by the monitor circuit 120 occurred. In oneembodiment, at block 1145, the NWAIT instruction is committed orretired.

The NWAIT instruction works in concert with the NMONITOR instruction toeither return an address being monitored (which was registered by theNMONITOR instruction) for which a triggering event has occurred or causethe core to enter an optimized state if a triggering event for anaddresses being monitored (which could potentially include multipleaddresses registered by the NMONITOR instruction) has not occurred.

FIG. 12 is a flow diagram of a process performed by a core to process anNMONITOR instruction followed by an NPOLL instruction, according to someembodiments. At block 1105, an NMONITOR instruction is fetched, wherethe NMONITOR instruction specifies an address to be monitored. In oneembodiment, the NMONITOR instruction is fetched from an instructionstorage 102. At block 1110, the fetched NMONITOR instruction is decodedby a decode circuit 104. At block 1115, the address specified by theNMONITOR instruction is retrieved. At block 1120, the NMONITORinstruction is executed by an execution circuit 106 to add an entry forthe specified address to be monitored into a data structure (e.g., armedtable 310) of a monitor circuit 120 and ensure (using a cache coherenceprotocol) that a coherency status of a cache line corresponding to thespecified address to be monitored is in a shared state, where themonitor circuit 120 is to enqueue the specified address to be monitoredinto a triggered queue 320 of the monitor circuit 120 in response to adetermination that a triggering event for the specified address to bemonitored occurred. In one embodiment, at block 1125, the NMONITORinstruction is committed or retired.

The NMONITOR instruction thus registers a specified address to bemonitored by the monitor circuit 120. The NMONITOR instruction may becalled multiple times, each time with a different address, to registermultiple addresses for monitoring. The number of addresses that can bemonitored simultaneously is only limited by the size of the datastructure (e.g., armed table 310).

At block 1130, an NPOLL instruction is fetched. In one embodiment, theNPOLL instruction is fetched from an instruction storage 102. At block1135, the fetched NPOLL instruction is decoded by a decode circuit 104.At block 1140, the NPOLL instruction is executed by an execution circuit106 to dequeue an address from a triggered queue 320 of a monitorcircuit 120 and return the dequeued address in response to adetermination that the triggered queue 320 is not empty and return anindication that a triggering event for an address being monitored by themonitor circuit 120 has not occurred in response to a determination thatthe triggered queue 320 is empty. In one embodiment, at block 1145, theWAIT instruction is committed or retired.

The NPOLL instruction works in concert with the NMONITOR instruction toeither return an address for which a triggering event has occurred(which was registered using the NMONITOR instruction) or returns anindication that a triggering event for an address being monitored hasnot occurred if a triggering event for an addresses being monitored(which could potentially include multiple addresses registered by theNMONITOR instruction) has not occurred.

Throughout the description, reference is made to an NMONITOR instructionand NWAIT/NPOLL instruction. It should be understood that thisnomenclature is provided by way of example, and that other embodimentsmay refer to these instructions using a different name.

Instruction Sets

An instruction set may include one or more instruction formats. A giveninstruction format may define various fields (e.g., number of bits,location of bits) to specify, among other things, the operation to beperformed (e.g., opcode) and the operand(s) on which that operation isto be performed and/or other data field(s) (e.g., mask). Someinstruction formats are further broken down though the definition ofinstruction templates (or subformats). For example, the instructiontemplates of a given instruction format may be defined to have differentsubsets of the instruction format's fields (the included fields aretypically in the same order, but at least some have different bitpositions because there are less fields included) and/or defined to havea given field interpreted differently. Thus, each instruction of an ISAis expressed using a given instruction format (and, if defined, in agiven one of the instruction templates of that instruction format) andincludes fields for specifying the operation and the operands. Forexample, an exemplary ADD instruction has a specific opcode and aninstruction format that includes an opcode field to specify that opcodeand operand fields to select operands (source1/destination and source2);and an occurrence of this ADD instruction in an instruction stream willhave specific contents in the operand fields that select specificoperands. A set of SIMD extensions referred to as the Advanced VectorExtensions (AVX) (AVX1 and AVX2) and using the Vector Extensions (VEX)coding scheme has been released and/or published (e.g., see Intel® 64and IA-32 Architectures Software Developer's Manual, September 2014; andsee Intel® Advanced Vector Extensions Programming Reference, October2014).

Exemplary Instruction Formats

Embodiments of the instruction(s) described herein may be embodied indifferent formats. Additionally, exemplary systems, architectures, andpipelines are detailed below. Embodiments of the instruction(s) may beexecuted on such systems, architectures, and pipelines, but are notlimited to those detailed.

Generic Vector Friendly Instruction Format

A vector friendly instruction format is an instruction format that issuited for vector instructions (e.g., there are certain fields specificto vector operations). While embodiments are described in which bothvector and scalar operations are supported through the vector friendlyinstruction format, alternative embodiments use only vector operationsthe vector friendly instruction format.

FIGS. 13A-13B are block diagrams illustrating a generic vector friendlyinstruction format and instruction templates thereof according toembodiments of the invention. FIG. 13A is a block diagram illustrating ageneric vector friendly instruction format and class A instructiontemplates thereof according to embodiments of the invention; while FIG.13B is a block diagram illustrating the generic vector friendlyinstruction format and class B instruction templates thereof accordingto embodiments of the invention. Specifically, a generic vector friendlyinstruction format 1300 for which are defined class A and class Binstruction templates, both of which include no memory access 1305instruction templates and memory access 1320 instruction templates. Theterm generic in the context of the vector friendly instruction formatrefers to the instruction format not being tied to any specificinstruction set.

While embodiments of the invention will be described in which the vectorfriendly instruction format supports the following: a 64 byte vectoroperand length (or size) with 32 bit (4 byte) or 64 bit (8 byte) dataelement widths (or sizes) (and thus, a 64 byte vector consists of either16 doubleword-size elements or alternatively, 8 quadword-size elements);a 64 byte vector operand length (or size) with 16 bit (2 byte) or 8 bit(1 byte) data element widths (or sizes); a 32 byte vector operand length(or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8bit (1 byte) data element widths (or sizes); and a 16 byte vectoroperand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit(2 byte), or 8 bit (1 byte) data element widths (or sizes); alternativeembodiments may support more, less and/or different vector operand sizes(e.g., 256 byte vector operands) with more, less, or different dataelement widths (e.g., 128 bit (16 byte) data element widths).

The class A instruction templates in FIG. 13A include: 1) within the nomemory access 1305 instruction templates there is shown a no memoryaccess, full round control type operation 1310 instruction template anda no memory access, data transform type operation 1315 instructiontemplate; and 2) within the memory access 1320 instruction templatesthere is shown a memory access, temporal 1325 instruction template and amemory access, non-temporal 1330 instruction template. The class Binstruction templates in FIG. 13B include: 1) within the no memoryaccess 1305 instruction templates there is shown a no memory access,write mask control, partial round control type operation 1312instruction template and a no memory access, write mask control, vsizetype operation 1317 instruction template; and 2) within the memoryaccess 1320 instruction templates there is shown a memory access, writemask control 1327 instruction template.

The generic vector friendly instruction format 1300 includes thefollowing fields listed below in the order illustrated in FIGS. 13A-13B.

Format field 1340—a specific value (an instruction format identifiervalue) in this field uniquely identifies the vector friendly instructionformat, and thus occurrences of instructions in the vector friendlyinstruction format in instruction streams. As such, this field isoptional in the sense that it is not needed for an instruction set thathas only the generic vector friendly instruction format.

Base operation field 1342—its content distinguishes different baseoperations.

Register index field 1344—its content, directly or through addressgeneration, specifies the locations of the source and destinationoperands, be they in registers or in memory. These include a sufficientnumber of bits to select N registers from a PxQ (e.g. 32×512, 16×128,32×1024, 64×1024) register file. While in one embodiment N may be up tothree sources and one destination register, alternative embodiments maysupport more or less sources and destination registers (e.g., maysupport up to two sources where one of these sources also acts as thedestination, may support up to three sources where one of these sourcesalso acts as the destination, may support up to two sources and onedestination).

Modifier field 1346—its content distinguishes occurrences ofinstructions in the generic vector instruction format that specifymemory access from those that do not; that is, between no memory access1305 instruction templates and memory access 1320 instruction templates.Memory access operations read and/or write to the memory hierarchy (insome cases specifying the source and/or destination addresses usingvalues in registers), while non-memory access operations do not (e.g.,the source and destinations are registers). While in one embodiment thisfield also selects between three different ways to perform memoryaddress calculations, alternative embodiments may support more, less, ordifferent ways to perform memory address calculations.

Augmentation operation field 1350—its content distinguishes which one ofa variety of different operations to be performed in addition to thebase operation. This field is context specific. In one embodiment of theinvention, this field is divided into a class field 1368, an alpha field1352, and a beta field 1354. The augmentation operation field 1350allows common groups of operations to be performed in a singleinstruction rather than 2, 3, or 4 instructions.

Scale field 1360—its content allows for the scaling of the index field'scontent for memory address generation (e.g., for address generation thatuses 2^(scale)* index+base).

Displacement Field 1362A—its content is used as part of memory addressgeneration (e.g., for address generation that uses 2^(scale)*index+base+displacement).

Displacement Factor Field 1362B (note that the juxtaposition ofdisplacement field 1362A directly over displacement factor field 1362Bindicates one or the other is used)—its content is used as part ofaddress generation; it specifies a displacement factor that is to bescaled by the size of a memory access (N)—where N is the number of bytesin the memory access (e.g., for address generation that uses 2^(scale)*index+base+scaled displacement). Redundant low-order bits are ignoredand hence, the displacement factor field's content is multiplied by thememory operands total size (N) in order to generate the finaldisplacement to be used in calculating an effective address. The valueof N is determined by the processor hardware at runtime based on thefull opcode field 1374 (described later herein) and the datamanipulation field 1354C. The displacement field 1362A and thedisplacement factor field 1362B are optional in the sense that they arenot used for the no memory access 1305 instruction templates and/ordifferent embodiments may implement only one or none of the two.

Data element width field 1364—its content distinguishes which one of anumber of data element widths is to be used (in some embodiments for allinstructions; in other embodiments for only some of the instructions).This field is optional in the sense that it is not needed if only onedata element width is supported and/or data element widths are supportedusing some aspect of the opcodes.

Write mask field 1370—its content controls, on a per data elementposition basis, whether that data element position in the destinationvector operand reflects the result of the base operation andaugmentation operation. Class A instruction templates supportmerging-writemasking, while class B instruction templates support bothmerging- and zeroing-writemasking. When merging, vector masks allow anyset of elements in the destination to be protected from updates duringthe execution of any operation (specified by the base operation and theaugmentation operation); in other one embodiment, preserving the oldvalue of each element of the destination where the corresponding maskbit has a 0. In contrast, when zeroing vector masks allow any set ofelements in the destination to be zeroed during the execution of anyoperation (specified by the base operation and the augmentationoperation); in one embodiment, an element of the destination is set to 0when the corresponding mask bit has a 0 value. A subset of thisfunctionality is the ability to control the vector length of theoperation being performed (that is, the span of elements being modified,from the first to the last one); however, it is not necessary that theelements that are modified be consecutive. Thus, the write mask field1370 allows for partial vector operations, including loads, stores,arithmetic, logical, etc. While embodiments of the invention aredescribed in which the write mask field's 1370 content selects one of anumber of write mask registers that contains the write mask to be used(and thus the write mask field's 1370 content indirectly identifies thatmasking to be performed), alternative embodiments instead or additionalallow the mask write field's 1370 content to directly specify themasking to be performed.

Immediate field 1372—its content allows for the specification of animmediate. This field is optional in the sense that is it not present inan implementation of the generic vector friendly format that does notsupport immediate and it is not present in instructions that do not usean immediate.

Class field 1368—its content distinguishes between different classes ofinstructions. With reference to FIGS. 13A-B, the contents of this fieldselect between class A and class B instructions. In FIGS. 13A-B, roundedcorner squares are used to indicate a specific value is present in afield (e.g., class A 1368A and class B 1368B for the class field 1368respectively in FIGS. 13A-B).

Instruction Templates of Class A

In the case of the non-memory access 1305 instruction templates of classA, the alpha field 1352 is interpreted as an RS field 1352A, whosecontent distinguishes which one of the different augmentation operationtypes are to be performed (e.g., round 1352A.1 and data transform1352A.2 are respectively specified for the no memory access, round typeoperation 1310 and the no memory access, data transform type operation1315 instruction templates), while the beta field 1354 distinguisheswhich of the operations of the specified type is to be performed. In theno memory access 1305 instruction templates, the scale field 1360, thedisplacement field 1362A, and the displacement scale filed 1362B are notpresent.

No-Memory Access Instruction Templates—Full Round Control Type Operation

In the no memory access full round control type operation 1310instruction template, the beta field 1354 is interpreted as a roundcontrol field 1354A, whose content(s) provide static rounding. While inthe described embodiments of the invention the round control field 1354Aincludes a suppress all floating point exceptions (SAE) field 1356 and around operation control field 1358, alternative embodiments may supportmay encode both these concepts into the same field or only have one orthe other of these concepts/fields (e.g., may have only the roundoperation control field 1358).

SAE field 1356—its content distinguishes whether or not to disable theexception event reporting; when the SAE field's 1356 content indicatessuppression is enabled, a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler.

Round operation control field 1358—its content distinguishes which oneof a group of rounding operations to perform (e.g., Round-up,Round-down, Round-towards-zero and Round-to-nearest). Thus, the roundoperation control field 1358 allows for the changing of the roundingmode on a per instruction basis. In one embodiment of the inventionwhere a processor includes a control register for specifying roundingmodes, the round operation control field's 1350 content overrides thatregister value.

No Memory Access Instruction Templates—Data Transform Type Operation

In the no memory access data transform type operation 1315 instructiontemplate, the beta field 1354 is interpreted as a data transform field1354B, whose content distinguishes which one of a number of datatransforms is to be performed (e.g., no data transform, swizzle,broadcast).

In the case of a memory access 1320 instruction template of class A, thealpha field 1352 is interpreted as an eviction hint field 1352B, whosecontent distinguishes which one of the eviction hints is to be used (inFIG. 13A, temporal 1352B.1 and non-temporal 1352B.2 are respectivelyspecified for the memory access, temporal 1325 instruction template andthe memory access, non-temporal 1330 instruction template), while thebeta field 1354 is interpreted as a data manipulation field 1354C, whosecontent distinguishes which one of a number of data manipulationoperations (also known as primitives) is to be performed (e.g., nomanipulation; broadcast; up conversion of a source; and down conversionof a destination). The memory access 1320 instruction templates includethe scale field 1360, and optionally the displacement field 1362A or thedisplacement scale field 1362B.

Vector memory instructions perform vector loads from and vector storesto memory, with conversion support. As with regular vector instructions,vector memory instructions transfer data from/to memory in a dataelement-wise fashion, with the elements that are actually transferred isdictated by the contents of the vector mask that is selected as thewrite mask.

Memory Access Instruction Templates—Temporal

Temporal data is data likely to be reused soon enough to benefit fromcaching. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

Memory Access Instruction Templates—Non-Temporal

Non-temporal data is data unlikely to be reused soon enough to benefitfrom caching in the 1st-level cache and should be given priority foreviction. This is, however, a hint, and different processors mayimplement it in different ways, including ignoring the hint entirely.

Instruction Templates of Class B

In the case of the instruction templates of class B, the alpha field1352 is interpreted as a write mask control (Z) field 1352C, whosecontent distinguishes whether the write masking controlled by the writemask field 1370 should be a merging or a zeroing.

In the case of the non-memory access 1305 instruction templates of classB, part of the beta field 1354 is interpreted as an RL field 1357A,whose content distinguishes which one of the different augmentationoperation types are to be performed (e.g., round 1357A.1 and vectorlength (VSIZE) 1357A.2 are respectively specified for the no memoryaccess, write mask control, partial round control type operation 1312instruction template and the no memory access, write mask control, VSIZEtype operation 1317 instruction template), while the rest of the betafield 1354 distinguishes which of the operations of the specified typeis to be performed. In the no memory access 1305 instruction templates,the scale field 1360, the displacement field 1362A, and the displacementscale filed 1362B are not present.

In the no memory access, write mask control, partial round control typeoperation 1310 instruction template, the rest of the beta field 1354 isinterpreted as a round operation field 1359A and exception eventreporting is disabled (a given instruction does not report any kind offloating-point exception flag and does not raise any floating pointexception handler).

Round operation control field 1359A—just as round operation controlfield 1358, its content distinguishes which one of a group of roundingoperations to perform (e.g., Round-up, Round-down, Round-towards-zeroand Round-to-nearest). Thus, the round operation control field 1359Aallows for the changing of the rounding mode on a per instruction basis.In one embodiment of the invention where a processor includes a controlregister for specifying rounding modes, the round operation controlfield's 1350 content overrides that register value.

In the no memory access, write mask control, VSIZE type operation 1317instruction template, the rest of the beta field 1354 is interpreted asa vector length field 1359B, whose content distinguishes which one of anumber of data vector lengths is to be performed on (e.g., 128, 256, or512 byte).

In the case of a memory access 1320 instruction template of class B,part of the beta field 1354 is interpreted as a broadcast field 1357B,whose content distinguishes whether or not the broadcast type datamanipulation operation is to be performed, while the rest of the betafield 1354 is interpreted the vector length field 1359B. The memoryaccess 1320 instruction templates include the scale field 1360, andoptionally the displacement field 1362A or the displacement scale field1362B.

With regard to the generic vector friendly instruction format 1300, afull opcode field 1374 is shown including the format field 1340, thebase operation field 1342, and the data element width field 1364. Whileone embodiment is shown where the full opcode field 1374 includes all ofthese fields, the full opcode field 1374 includes less than all of thesefields in embodiments that do not support all of them. The full opcodefield 1374 provides the operation code (opcode).

The augmentation operation field 1350, the data element width field1364, and the write mask field 1370 allow these features to be specifiedon a per instruction basis in the generic vector friendly instructionformat.

The combination of write mask field and data element width field createtyped instructions in that they allow the mask to be applied based ondifferent data element widths.

The various instruction templates found within class A and class B arebeneficial in different situations. In some embodiments of theinvention, different processors or different cores within a processormay support only class A, only class B, or both classes. For instance, ahigh performance general purpose out-of-order core intended forgeneral-purpose computing may support only class B, a core intendedprimarily for graphics and/or scientific (throughput) computing maysupport only class A, and a core intended for both may support both (ofcourse, a core that has some mix of templates and instructions from bothclasses but not all templates and instructions from both classes iswithin the purview of the invention). Also, a single processor mayinclude multiple cores, all of which support the same class or in whichdifferent cores support different class. For instance, in a processorwith separate graphics and general purpose cores, one of the graphicscores intended primarily for graphics and/or scientific computing maysupport only class A, while one or more of the general purpose cores maybe high performance general purpose cores with out of order executionand register renaming intended for general-purpose computing thatsupport only class B. Another processor that does not have a separategraphics core, may include one more general purpose in-order orout-of-order cores that support both class A and class B. Of course,features from one class may also be implement in the other class indifferent embodiments of the invention. Programs written in a high levellanguage would be put (e.g., just in time compiled or staticallycompiled) into an variety of different executable forms, including: 1) aform having only instructions of the class(es) supported by the targetprocessor for execution; or 2) a form having alternative routineswritten using different combinations of the instructions of all classesand having control flow code that selects the routines to execute basedon the instructions supported by the processor which is currentlyexecuting the code.

Exemplary Specific Vector Friendly Instruction Format

FIG. 14A is a block diagram illustrating an exemplary specific vectorfriendly instruction format according to embodiments of the invention.FIG. 14A shows a specific vector friendly instruction format 1400 thatis specific in the sense that it specifies the location, size,interpretation, and order of the fields, as well as values for some ofthose fields. The specific vector friendly instruction format 1400 maybe used to extend the x86 instruction set, and thus some of the fieldsare similar or the same as those used in the existing x86 instructionset and extension thereof (e.g., AVX). This format remains consistentwith the prefix encoding field, real opcode byte field, MOD R/M field,SIB field, displacement field, and immediate fields of the existing x86instruction set with extensions. The fields from FIG. 13 into which thefields from FIG. 14A map are illustrated.

It should be understood that, although embodiments of the invention aredescribed with reference to the specific vector friendly instructionformat 1400 in the context of the generic vector friendly instructionformat 1300 for illustrative purposes, the invention is not limited tothe specific vector friendly instruction format 1400 except whereclaimed. For example, the generic vector friendly instruction format1300 contemplates a variety of possible sizes for the various fields,while the specific vector friendly instruction format 1400 is shown ashaving fields of specific sizes. By way of specific example, while thedata element width field 1364 is illustrated as a one bit field in thespecific vector friendly instruction format 1400, the invention is notso limited (that is, the generic vector friendly instruction format 1300contemplates other sizes of the data element width field 1364).

The generic vector friendly instruction format 1300 includes thefollowing fields listed below in the order illustrated in FIG. 14A.

EVEX Prefix (Bytes 0-3) 1402—is encoded in a four-byte form.

Format Field 1340 (EVEX Byte 0, bits [7:0])—the first byte (EVEX Byte 0)is the format field 1340 and it contains 0×62 (the unique value used fordistinguishing the vector friendly instruction format in one embodimentof the invention).

The second-fourth bytes (EVEX Bytes 1-3) include a number of bit fieldsproviding specific capability.

REX field 1405 (EVEX Byte 1, bits [7-5])—consists of a EVEX.R bit field(EVEX Byte 1, bit [7]—R), EVEX.X bit field (EVEX byte 1, bit [6]—X), and1357BEX byte 1, bit[5]—B). The EVEX.R, EVEX.X, and EVEX.B bit fieldsprovide the same functionality as the corresponding VEX bit fields, andare encoded using 1s complement form, i.e. ZMM0 is encoded as 1111B,ZMM15 is encoded as 0000B. Other fields of the instructions encode thelower three bits of the register indexes as is known in the art (rrr,xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed by addingEVEX.R, EVEX.X, and EVEX.B.

REX′ field 1310—this is the first part of the REX′ field 1310 and is theEVEX.R′ bit field (EVEX Byte 1, bit [4]—R′) that is used to encodeeither the upper 16 or lower 16 of the extended 32 register set. In oneembodiment of the invention, this bit, along with others as indicatedbelow, is stored in bit inverted format to distinguish (in thewell-known x86 32-bit mode) from the BOUND instruction, whose realopcode byte is 62, but does not accept in the MOD R/M field (describedbelow) the value of 11 in the MOD field; alternative embodiments of theinvention do not store this and the other indicated bits below in theinverted format. A value of 1 is used to encode the lower 16 registers.In other words, R′Rrrr is formed by combining EVEX.R′, EVEX.R, and theother RRR from other fields.

Opcode map field 1415 (EVEX byte 1, bits [3:0]—mmmm)—its content encodesan implied leading opcode byte (0F, 0F 38, or 0F 3).

Data element width field 1364 (EVEX byte 2, bit [7]—W)—is represented bythe notation EVEX.W. EVEX.W is used to define the granularity (size) ofthe datatype (either 32-bit data elements or 64-bit data elements).

EVEX.vvvv 1420 (EVEX Byte 2, bits [6:3]—vvvv)—the role of EVEX.vvvv mayinclude the following: 1) EVEX.vvvv encodes the first source registeroperand, specified in inverted (1s complement) form and is valid forinstructions with 2 or more source operands; 2) EVEX.vvvv encodes thedestination register operand, specified in is complement form forcertain vector shifts; or 3) EVEX.vvvv does not encode any operand, thefield is reserved and should contain 1111 b. Thus, EVEX.vvvv field 1420encodes the 4 low-order bits of the first source register specifierstored in inverted (1s complement) form. Depending on the instruction,an extra different EVEX bit field is used to extend the specifier sizeto 32 registers.

EVEX.U 1368 Class field (EVEX byte 2, bit [2]—U)—If EVEX.U=0, itindicates class A or EVEX.U0; if EVEX.U=1, it indicates class B orEVEX.U1.

Prefix encoding field 1425 (EVEX byte 2, bits [1:0]—pp)—providesadditional bits for the base operation field. In addition to providingsupport for the legacy SSE instructions in the EVEX prefix format, thisalso has the benefit of compacting the SIMD prefix (rather thanrequiring a byte to express the SIMD prefix, the EVEX prefix requiresonly 2 bits). In one embodiment, to support legacy SSE instructions thatuse a SIMD prefix (66H, F2H, F3H) in both the legacy format and in theEVEX prefix format, these legacy SIMD prefixes are encoded into the SIMDprefix encoding field; and at runtime are expanded into the legacy SIMDprefix prior to being provided to the decoder's PLA (so the PLA canexecute both the legacy and EVEX format of these legacy instructionswithout modification). Although newer instructions could use the EVEXprefix encoding field's content directly as an opcode extension, certainembodiments expand in a similar fashion for consistency but allow fordifferent meanings to be specified by these legacy SIMD prefixes. Analternative embodiment may redesign the PLA to support the 2 bit SIMDprefix encodings, and thus not require the expansion.

Alpha field 1352 (EVEX byte 3, bit [7]—EH; also known as EVEX.EH,EVEX.rs, EVEX.RL, EVEX.write mask control, and EVEX.N; also illustratedwith α)—as previously described, this field is context specific.

Beta field 1354 (EVEX byte 3, bits [6:4]—SSS, also known asEVEX._(S-02), EVEX.r₂₋₀, EVEX.rr1, EVEX.LL0, EVEX.LLB; also illustratedwith βββ)—as previously described, this field is context specific.

REX′ field 1310—this is the remainder of the REX′ field and is theEVEX.V′ bit field (EVEX Byte 3, bit [3]—V′) that may be used to encodeeither the upper 16 or lower 16 of the extended 32 register set. Thisbit is stored in bit inverted format. A value of 1 is used to encode thelower 16 registers. In other words, V′VVVV is formed by combiningEVEX.V′, EVEX.vvvv.

Write mask field 1370 (EVEX byte 3, bits [2:0]-kkk)—its contentspecifies the index of a register in the write mask registers aspreviously described. In one embodiment of the invention, the specificvalue EVEX.kkk=000 has a special behavior implying no write mask is usedfor the particular instruction (this may be implemented in a variety ofways including the use of a write mask hardwired to all ones or hardwarethat bypasses the masking hardware).

Real Opcode Field 1430 (Byte 4) is also known as the opcode byte. Partof the opcode is specified in this field.

MOD R/M Field 1440 (Byte 5) includes MOD field 1442, Reg field 1444, andR/M field 1446. As previously described, the MOD field's 1442 contentdistinguishes between memory access and non-memory access operations.The role of Reg field 1444 can be summarized to two situations: encodingeither the destination register operand or a source register operand, orbe treated as an opcode extension and not used to encode any instructionoperand. The role of R/M field 1446 may include the following: encodingthe instruction operand that references a memory address, or encodingeither the destination register operand or a source register operand.

Scale, Index, Base (SIB) Byte (Byte 6)—As previously described, thescale field's 1350 content is used for memory address generation.SIB.xxx 1454 and SIB.bbb 1456—the contents of these fields have beenpreviously referred to with regard to the register indexes Xxxx andBbbb.

Displacement field 1362A (Bytes 7-10)—when MOD field 1442 contains 10,bytes 7-10 are the displacement field 1362A, and it works the same asthe legacy 32-bit displacement (disp32) and works at byte granularity.

Displacement factor field 1362B (Byte 7)—when MOD field 1442 contains01, byte 7 is the displacement factor field 1362B. The location of thisfield is that same as that of the legacy x86 instruction set 8-bitdisplacement (disp8), which works at byte granularity. Since disp8 issign extended, it can only address between −128 and 127 bytes offsets;in terms of 64 byte cache lines, disp8 uses 8 bits that can be set toonly four really useful values −128, −64, 0, and 64; since a greaterrange is often needed, disp32 is used; however, disp32 requires 4 bytes.In contrast to disp8 and disp32, the displacement factor field 1362B isa reinterpretation of disp8; when using displacement factor field 1362B,the actual displacement is determined by the content of the displacementfactor field multiplied by the size of the memory operand access (N).This type of displacement is referred to as disp8*N. This reduces theaverage instruction length (a single byte of used for the displacementbut with a much greater range). Such compressed displacement is based onthe assumption that the effective displacement is multiple of thegranularity of the memory access, and hence, the redundant low-orderbits of the address offset do not need to be encoded. In other words,the displacement factor field 1362B substitutes the legacy x86instruction set 8-bit displacement. Thus, the displacement factor field1362B is encoded the same way as an x86 instruction set 8-bitdisplacement (so no changes in the ModRM/SIB encoding rules) with theonly exception that disp8 is overloaded to disp8*N. In other words,there are no changes in the encoding rules or encoding lengths but onlyin the interpretation of the displacement value by hardware (which needsto scale the displacement by the size of the memory operand to obtain abyte-wise address offset). Immediate field 1372 operates as previouslydescribed.

Full Opcode Field

FIG. 14B is a block diagram illustrating the fields of the specificvector friendly instruction format 1400 that make up the full opcodefield 1374 according to one embodiment of the invention. Specifically,the full opcode field 1374 includes the format field 1340, the baseoperation field 1342, and the data element width (W) field 1364. Thebase operation field 1342 includes the prefix encoding field 1425, theopcode map field 1415, and the real opcode field 1430.

Register Index Field

FIG. 14C is a block diagram illustrating the fields of the specificvector friendly instruction format 1400 that make up the register indexfield 1344 according to one embodiment of the invention. Specifically,the register index field 1344 includes the REX field 1405, the REX′field 1410, the MODR/M.reg field 1444, the MODR/M.r/m field 1446, theVVVV field 1420, xxx field 1454, and the bbb field 1456.

Augmentation Operation Field

FIG. 14D is a block diagram illustrating the fields of the specificvector friendly instruction format 1400 that make up the augmentationoperation field 1350 according to one embodiment of the invention. Whenthe class (U) field 1368 contains 0, it signifies EVEX.U0 (class A 1368A); when it contains 1, it signifies EVEX.U1 (class B 1368 B). When U=0and the MOD field 1442 contains 11 (signifying a no memory accessoperation), the alpha field 1352 (EVEX byte 3, bit [7]—EH) isinterpreted as the rs field 1352A. When the rs field 1352A contains a 1(round 1352A.1), the beta field 1354 (EVEX byte 3, bits [6:4]—SSS) isinterpreted as the round control field 1354A. The round control field1354A includes a one bit SAE field 1356 and a two bit round operationfield 1358. When the rs field 1352A contains a 0 (data transform1352A.2), the beta field 1354 (EVEX byte 3, bits [6:4]—SSS) isinterpreted as a three bit data transform field 1354B. When U=0 and theMOD field 1442 contains 00, 01, or 10 (signifying a memory accessoperation), the alpha field 1352 (EVEX byte 3, bit [7]—EH) isinterpreted as the eviction hint (EH) field 1352B and the beta field1354 (EVEX byte 3, bits [6:4]—SSS) is interpreted as a three bit datamanipulation field 1354C.

When U=1, the alpha field 1352 (EVEX byte 3, bit [7]—EH) is interpretedas the write mask control (Z) field 1352 C. When U=1 and the MOD field1442 contains 11 (signifying a no memory access operation), part of thebeta field 1354 (EVEX byte 3, bit [4]—S₀) is interpreted as the RL field1357A; when it contains a 1 (round 1357A.1) the rest of the beta field1354 (EVEX byte 3, bit [6-5]—S₂₋₁) is interpreted as the round operationfield 1359A, while when the RL field 1357A contains a 0 (VSIZE 1357.A2)the rest of the beta field 1354 (EVEX byte 3, bit [6-5]—S₂₋₁) isinterpreted as the vector length field 1359B (EVEX byte 3, bit[6-5]—L₁₋₀). When U=1 and the MOD field 1442 contains 00, 01, or 10(signifying a memory access operation), the beta field 1354 (EVEX byte3, bits [6:4]—SSS) is interpreted as the vector length field 1359B (EVEXbyte 3, bit [6-5]—L₁₋₀) and the broadcast field 1357B (EVEX byte 3, bit[4]—B).

Exemplary Register Architecture

FIG. 15 is a block diagram of a register architecture 1500 according toone embodiment of the invention. In the embodiment illustrated, thereare 32 vector registers 1510 that are 512 bits wide; these registers arereferenced as zmm0 through zmm31. The lower order 256 bits of the lower16 zmm registers are overlaid on registers ymm0-16. The lower order 128bits of the lower 16 zmm registers (the lower order 128 bits of the ymmregisters) are overlaid on registers xmm0-15. The specific vectorfriendly instruction format 1400 operates on these overlaid registerfile as illustrated in the below tables.

Adjustable Vector Length Class Operations Registers InstructionTemplates A (FIG. 1310, 1315, zmm registers (the vector length is thatdo not include the 13A; 1325, 1330 64 byte) vector length field 1359B U= 0) B (FIG. 1312 zmm registers (the vector length is 13B; 64 byte) U= 1) Instruction templates that B (FIG. 1317, 1327 zmm, ymm, or xmmregisters (the do include the vector 13B; vector length is 64 byte, 32byte, or length field 1359B U = 1) 16 byte) depending on the vectorlength field 1359B

In other words, the vector length field 1359B selects between a maximumlength and one or more other shorter lengths, where each such shorterlength is half the length of the preceding length; and instructionstemplates without the vector length field 1359B operate on the maximumvector length. Further, in one embodiment, the class B instructiontemplates of the specific vector friendly instruction format 1400operate on packed or scalar single/double-precision floating point dataand packed or scalar integer data. Scalar operations are operationsperformed on the lowest order data element position in an zmm/ymm/xmmregister; the higher order data element positions are either left thesame as they were prior to the instruction or zeroed depending on theembodiment.

Write mask registers 1515—in the embodiment illustrated, there are 8write mask registers (k0 through k7), each 64 bits in size. In analternate embodiment, the write mask registers 1515 are 16 bits in size.As previously described, in one embodiment of the invention, the vectormask register k0 cannot be used as a write mask; when the encoding thatwould normally indicate k0 is used for a write mask, it selects ahardwired write mask of 0xFFFF, effectively disabling write masking forthat instruction.

General-purpose registers 1525—in the embodiment illustrated, there aresixteen 64-bit general-purpose registers that are used along with theexisting x86 addressing modes to address memory operands. Theseregisters are referenced by the names RAX, RBX, RCX, RDX, RBP, RSI, RDI,RSP, and R8 through R15.

Scalar floating point stack register file (x87 stack) 1545, on which isaliased the MMX packed integer flat register file 1550—in the embodimentillustrated, the x87 stack is an eight-element stack used to performscalar floating-point operations on 32/64/80-bit floating point datausing the x87 instruction set extension; while the MMX registers areused to perform operations on 64-bit packed integer data, as well as tohold operands for some operations performed between the MMX and XMMregisters.

Alternative embodiments of the invention may use wider or narrowerregisters. Additionally, alternative embodiments of the invention mayuse more, less, or different register files and registers.

Exemplary Core Architectures, Processors, and Computer Architectures

Processor cores may be implemented in different ways, for differentpurposes, and in different processors. For instance, implementations ofsuch cores may include: 1) a general purpose in-order core intended forgeneral-purpose computing; 2) a high performance general purposeout-of-order core intended for general-purpose computing; 3) a specialpurpose core intended primarily for graphics and/or scientific(throughput) computing. Implementations of different processors mayinclude: 1) a CPU including one or more general purpose in-order coresintended for general-purpose computing and/or one or more generalpurpose out-of-order cores intended for general-purpose computing; and2) a coprocessor including one or more special purpose cores intendedprimarily for graphics and/or scientific (throughput). Such differentprocessors lead to different computer system architectures, which mayinclude: 1) the coprocessor on a separate chip from the CPU; 2) thecoprocessor on a separate die in the same package as a CPU; 3) thecoprocessor on the same die as a CPU (in which case, such a coprocessoris sometimes referred to as special purpose logic, such as integratedgraphics and/or scientific (throughput) logic, or as special purposecores); and 4) a system on a chip that may include on the same die thedescribed CPU (sometimes referred to as the application core(s) orapplication processor(s)), the above described coprocessor, andadditional functionality. Exemplary core architectures are describednext, followed by descriptions of exemplary processors and computerarchitectures.

Exemplary Core Architectures In-order and Out-of-Order Core BlockDiagram

FIG. 16A is a block diagram illustrating both an exemplary in-orderpipeline and an exemplary register renaming, out-of-orderissue/execution pipeline according to embodiments of the invention. FIG.16B is a block diagram illustrating both an exemplary embodiment of anin-order architecture core and an exemplary register renaming,out-of-order issue/execution architecture core to be included in aprocessor according to embodiments of the invention. The solid linedboxes in FIGS. 16A-B illustrate the in-order pipeline and in-order core,while the optional addition of the dashed lined boxes illustrates theregister renaming, out-of-order issue/execution pipeline and core. Giventhat the in-order aspect is a subset of the out-of-order aspect, theout-of-order aspect will be described.

In FIG. 16A, a processor pipeline 1600 includes a fetch stage 1602, alength decode stage 1604, a decode stage 1606, an allocation stage 1608,a renaming stage 1610, a scheduling (also known as a dispatch or issue)stage 1612, a register read/memory read stage 1614, an execute stage1616, a write back/memory write stage 1618, an exception handling stage1622, and a commit stage 1624.

FIG. 16B shows processor core 1690 including a front end unit 1630coupled to an execution engine unit 1650, and both are coupled to amemory unit 1670. The core 1690 may be a reduced instruction setcomputing (RISC) core, a complex instruction set computing (CISC) core,a very long instruction word (VLIW) core, or a hybrid or alternativecore type. As yet another option, the core 1690 may be a special-purposecore, such as, for example, a network or communication core, compressionengine, coprocessor core, general purpose computing graphics processingunit (GPGPU) core, graphics core, or the like.

The front end unit 1630 includes a branch prediction unit 1632 coupledto an instruction cache unit 1634, which is coupled to an instructiontranslation lookaside buffer (TLB) 1636, which is coupled to aninstruction fetch unit 1638, which is coupled to a decode unit 1640. Thedecode unit 1640 (or decoder) may decode instructions, and generate asan output one or more micro-operations, micro-code entry points,microinstructions, other instructions, or other control signals, whichare decoded from, or which otherwise reflect, or are derived from, theoriginal instructions. The decode unit 1640 may be implemented usingvarious different mechanisms. Examples of suitable mechanisms include,but are not limited to, look-up tables, hardware implementations,programmable logic arrays (PLAs), microcode read only memories (ROMs),etc. In one embodiment, the core 1690 includes a microcode ROM or othermedium that stores microcode for certain macroinstructions (e.g., indecode unit 1640 or otherwise within the front end unit 1630). Thedecode unit 1640 is coupled to a rename/allocator unit 1652 in theexecution engine unit 1650.

The execution engine unit 1650 includes the rename/allocator unit 1652coupled to a retirement unit 1654 and a set of one or more schedulerunit(s) 1656. The scheduler unit(s) 1656 represents any number ofdifferent schedulers, including reservations stations, centralinstruction window, etc. The scheduler unit(s) 1656 is coupled to thephysical register file(s) unit(s) 1658. Each of the physical registerfile(s) units 1658 represents one or more physical register files,different ones of which store one or more different data types, such asscalar integer, scalar floating point, packed integer, packed floatingpoint, vector integer, vector floating point, status (e.g., aninstruction pointer that is the address of the next instruction to beexecuted), etc. In one embodiment, the physical register file(s) unit1658 comprises a vector registers unit, a write mask registers unit, anda scalar registers unit. These register units may provide architecturalvector registers, vector mask registers, and general purpose registers.The physical register file(s) unit(s) 1658 is overlapped by theretirement unit 1654 to illustrate various ways in which registerrenaming and out-of-order execution may be implemented (e.g., using areorder buffer(s) and a retirement register file(s); using a futurefile(s), a history buffer(s), and a retirement register file(s); using aregister maps and a pool of registers; etc.). The retirement unit 1654and the physical register file(s) unit(s) 1658 are coupled to theexecution cluster(s) 1660. The execution cluster(s) 1660 includes a setof one or more execution units 1662 and a set of one or more memoryaccess units 1664. The execution units 1662 may perform variousoperations (e.g., shifts, addition, subtraction, multiplication) and onvarious types of data (e.g., scalar floating point, packed integer,packed floating point, vector integer, vector floating point). Whilesome embodiments may include a number of execution units dedicated tospecific functions or sets of functions, other embodiments may includeonly one execution unit or multiple execution units that all perform allfunctions. The scheduler unit(s) 1656, physical register file(s) unit(s)1658, and execution cluster(s) 1660 are shown as being possibly pluralbecause certain embodiments create separate pipelines for certain typesof data/operations (e.g., a scalar integer pipeline, a scalar floatingpoint/packed integer/packed floating point/vector integer/vectorfloating point pipeline, and/or a memory access pipeline that each havetheir own scheduler unit, physical register file(s) unit, and/orexecution cluster—and in the case of a separate memory access pipeline,certain embodiments are implemented in which only the execution clusterof this pipeline has the memory access unit(s) 1664). It should also beunderstood that where separate pipelines are used, one or more of thesepipelines may be out-of-order issue/execution and the rest in-order.

The set of memory access units 1664 is coupled to the memory unit 1670,which includes a data TLB unit 1672 coupled to a data cache unit 1674coupled to a level 2 (L2) cache unit 1676. In one exemplary embodiment,the memory access units 1664 may include a load unit, a store addressunit, and a store data unit, each of which is coupled to the data TLBunit 1672 in the memory unit 1670. The instruction cache unit 1634 isfurther coupled to a level 2 (L2) cache unit 1676 in the memory unit1670. The L2 cache unit 1676 is coupled to one or more other levels ofcache and eventually to a main memory.

By way of example, the exemplary register renaming, out-of-orderissue/execution core architecture may implement the pipeline 1600 asfollows: 1) the instruction fetch 1638 performs the fetch and lengthdecoding stages 1602 and 1604; 2) the decode unit 1640 performs thedecode stage 1606; 3) the rename/allocator unit 1652 performs theallocation stage 1608 and renaming stage 1610; 4) the scheduler unit(s)1656 performs the schedule stage 1612; 5) the physical register file(s)unit(s) 1658 and the memory unit 1670 perform the register read/memoryread stage 1614; the execution cluster 1660 perform the execute stage1616; 6) the memory unit 1670 and the physical register file(s) unit(s)1658 perform the write back/memory write stage 1618; 7) various unitsmay be involved in the exception handling stage 1622; and 8) theretirement unit 1654 and the physical register file(s) unit(s) 1658perform the commit stage 1624.

The core 1690 may support one or more instructions sets (e.g., the x86instruction set (with some extensions that have been added with newerversions); the MIPS instruction set of MIPS Technologies of Sunnyvale,Calif.; the ARM instruction set (with optional additional extensionssuch as NEON) of ARM Holdings of Sunnyvale, Calif.), including theinstruction(s) described herein. In one embodiment, the core 1690includes logic to support a packed data instruction set extension (e.g.,AVX1, AVX2), thereby allowing the operations used by many multimediaapplications to be performed using packed data.

It should be understood that the core may support multithreading(executing two or more parallel sets of operations or threads), and maydo so in a variety of ways including time sliced multithreading,simultaneous multithreading (where a single physical core provides alogical core for each of the threads that physical core issimultaneously multithreading), or a combination thereof (e.g., timesliced fetching and decoding and simultaneous multithreading thereaftersuch as in the Intel® Hyperthreading™ technology).

While register renaming is described in the context of out-of-orderexecution, it should be understood that register renaming may be used inan in-order architecture. While the illustrated embodiment of theprocessor also includes separate instruction and data cache units1634/1674 and a shared L2 cache unit 1676, alternative embodiments mayhave a single internal cache for both instructions and data, such as,for example, a Level 1 (L1) internal cache, or multiple levels ofinternal cache. In some embodiments, the system may include acombination of an internal cache and an external cache that is externalto the core and/or the processor. Alternatively, all of the cache may beexternal to the core and/or the processor.

Specific Exemplary In-Order Core Architecture

FIGS. 17A-B illustrate a block diagram of a more specific exemplaryin-order core architecture, which core would be one of several logicblocks (including other cores of the same type and/or different types)in a chip. The logic blocks communicate through a high-bandwidthinterconnect network (e.g., a ring network) with some fixed functionlogic, memory I/O interfaces, and other necessary I/O logic, dependingon the application.

FIG. 17A is a block diagram of a single processor core, along with itsconnection to the on-die interconnect network 1702 and with its localsubset of the Level 2 (L2) cache 1704, according to embodiments of theinvention. In one embodiment, an instruction decoder 1700 supports thex86 instruction set with a packed data instruction set extension. An L1cache 1706 allows low-latency accesses to cache memory into the scalarand vector units. While in one embodiment (to simplify the design), ascalar unit 1708 and a vector unit 1710 use separate register sets(respectively, scalar registers 1712 and vector registers 1714) and datatransferred between them is written to memory and then read back in froma level 1 (L1) cache 1706, alternative embodiments of the invention mayuse a different approach (e.g., use a single register set or include acommunication path that allow data to be transferred between the tworegister files without being written and read back).

The local subset of the L2 cache 1704 is part of a global L2 cache thatis divided into separate local subsets, one per processor core. Eachprocessor core has a direct access path to its own local subset of theL2 cache 1704. Data read by a processor core is stored in its L2 cachesubset 1704 and can be accessed quickly, in parallel with otherprocessor cores accessing their own local L2 cache subsets. Data writtenby a processor core is stored in its own L2 cache subset 1704 and isflushed from other subsets, if necessary. The ring network ensurescoherency for shared data. The ring network is bi-directional to allowagents such as processor cores, L2 caches and other logic blocks tocommunicate with each other within the chip. Each ring data-path is1012-bits wide per direction.

FIG. 17B is an expanded view of part of the processor core in FIG. 17Aaccording to embodiments of the invention. FIG. 17B includes an L1 datacache 1706A part of the L1 cache 1704, as well as more detail regardingthe vector unit 1710 and the vector registers 1714. Specifically, thevector unit 1710 is a 16-wide vector processing unit (VPU) (see the16-wide ALU 1728), which executes one or more of integer,single-precision float, and double-precision float instructions. The VPUsupports swizzling the register inputs with swizzle unit 1720, numericconversion with numeric convert units 1722A-B, and replication withreplication unit 1724 on the memory input. Write mask registers 1726allow predicating resulting vector writes.

FIG. 18 is a block diagram of a processor 1800 that may have more thanone core, may have an integrated memory controller, and may haveintegrated graphics according to embodiments of the invention. The solidlined boxes in FIG. 18 illustrate a processor 1800 with a single core1802A, a system agent 1810, a set of one or more bus controller units1816, while the optional addition of the dashed lined boxes illustratesan alternative processor 1800 with multiple cores 1802A-N, a set of oneor more integrated memory controller unit(s) 1814 in the system agentunit 1810, and special purpose logic 1808.

Thus, different implementations of the processor 1800 may include: 1) aCPU with the special purpose logic 1808 being integrated graphics and/orscientific (throughput) logic (which may include one or more cores), andthe cores 1802A-N being one or more general purpose cores (e.g., generalpurpose in-order cores, general purpose out-of-order cores, acombination of the two); 2) a coprocessor with the cores 1802A-N being alarge number of special purpose cores intended primarily for graphicsand/or scientific (throughput); and 3) a coprocessor with the cores1802A-N being a large number of general purpose in-order cores. Thus,the processor 1800 may be a general-purpose processor, coprocessor orspecial-purpose processor, such as, for example, a network orcommunication processor, compression engine, graphics processor, GPGPU(general purpose graphics processing unit), a high-throughput manyintegrated core (MIC) coprocessor (including 30 or more cores), embeddedprocessor, or the like. The processor may be implemented on one or morechips. The processor 1800 may be a part of and/or may be implemented onone or more substrates using any of a number of process technologies,such as, for example, BiCMOS, CMOS, or NMOS.

The memory hierarchy includes one or more levels of cache within thecores, a set or one or more shared cache units 1806, and external memory(not shown) coupled to the set of integrated memory controller units1814. The set of shared cache units 1806 may include one or moremid-level caches, such as level 2 (L2), level 3 (L3), level 4 (L4), orother levels of cache, a last level cache (LLC), and/or combinationsthereof. While in one embodiment a ring based interconnect unit 1812interconnects the integrated graphics logic 1808 (integrated graphicslogic 1808 is an example of and is also referred to herein as specialpurpose logic), the set of shared cache units 1806, and the system agentunit 1810/integrated memory controller unit(s) 1814, alternativeembodiments may use any number of well-known techniques forinterconnecting such units. In one embodiment, coherency is maintainedbetween one or more cache units 1806 and cores 1802-A-N.

In some embodiments, one or more of the cores 1802A-N are capable ofmulti-threading. The system agent 1810 includes those componentscoordinating and operating cores 1802A-N. The system agent unit 1810 mayinclude for example a power control unit (PCU) and a display unit. ThePCU may be or include logic and components needed for regulating thepower state of the cores 1802A-N and the integrated graphics logic 1808.The display unit is for driving one or more externally connecteddisplays.

The cores 1802A-N may be homogenous or heterogeneous in terms ofarchitecture instruction set; that is, two or more of the cores 1802A-Nmay be capable of execution the same instruction set, while others maybe capable of executing only a subset of that instruction set or adifferent instruction set.

Exemplary Computer Architectures

FIGS. 19-22 are block diagrams of exemplary computer architectures.Other system designs and configurations known in the arts for laptops,desktops, handheld PCs, personal digital assistants, engineeringworkstations, servers, network devices, network hubs, switches, embeddedprocessors, digital signal processors (DSPs), graphics devices, videogame devices, set-top boxes, micro controllers, cell phones, portablemedia players, hand held devices, and various other electronic devices,are also suitable. In general, a huge variety of systems or electronicdevices capable of incorporating a processor and/or other executionlogic as disclosed herein are generally suitable.

Referring now to FIG. 19, shown is a block diagram of a system 1900 inaccordance with one embodiment of the present invention. The system 1900may include one or more processors 1910, 1915, which are coupled to acontroller hub 1920. In one embodiment, the controller hub 1920 includesa graphics memory controller hub (GMCH) 1990 and an Input/Output Hub(IOH) 1950 (which may be on separate chips); the GMCH 1990 includesmemory and graphics controllers to which are coupled memory 1940 and acoprocessor 1945; the IOH 1950 couples input/output (I/O) devices 1960to the GMCH 1990. Alternatively, one or both of the memory and graphicscontrollers are integrated within the processor (as described herein),the memory 1940 and the coprocessor 1945 are coupled directly to theprocessor 1910, and the controller hub 1920 in a single chip with theIOH 1950.

The optional nature of additional processors 1915 is denoted in FIG. 19with broken lines. Each processor 1910, 1915 may include one or more ofthe processing cores described herein and may be some version of theprocessor 1800.

The memory 1940 may be, for example, dynamic random access memory(DRAM), phase change memory (PCM), or a combination of the two. For atleast one embodiment, the controller hub 1920 communicates with theprocessor(s) 1910, 1915 via a multi-drop bus, such as a frontside bus(FSB), point-to-point interface such as QuickPath Interconnect (QPI), orsimilar connection 1995.

In one embodiment, the coprocessor 1945 is a special-purpose processor,such as, for example, a high-throughput MIC processor, a network orcommunication processor, compression engine, graphics processor, GPGPU,embedded processor, or the like. In one embodiment, controller hub 1920may include an integrated graphics accelerator.

There can be a variety of differences between the physical resources1910, 1915 in terms of a spectrum of metrics of merit includingarchitectural, microarchitectural, thermal, power consumptioncharacteristics, and the like.

In one embodiment, the processor 1910 executes instructions that controldata processing operations of a general type. Embedded within theinstructions may be coprocessor instructions. The processor 1910recognizes these coprocessor instructions as being of a type that shouldbe executed by the attached coprocessor 1945. Accordingly, the processor1910 issues these coprocessor instructions (or control signalsrepresenting coprocessor instructions) on a coprocessor bus or otherinterconnect, to coprocessor 1945. Coprocessor(s) 1945 accept andexecute the received coprocessor instructions.

Referring now to FIG. 20, shown is a block diagram of a first morespecific exemplary system 2000 in accordance with an embodiment of thepresent invention. As shown in FIG. 20, multiprocessor system 2000 is apoint-to-point interconnect system, and includes a first processor 2070and a second processor 2080 coupled via a point-to-point interconnect2050. Each of processors 2070 and 2080 may be some version of theprocessor 1800. In one embodiment of the invention, processors 2070 and2080 are respectively processors 1910 and 1915, while coprocessor 2038is coprocessor 1945. In another embodiment, processors 2070 and 2080 arerespectively processor 1910 coprocessor 1945.

Processors 2070 and 2080 are shown including integrated memorycontroller (IMC) units 2072 and 2082, respectively. Processor 2070 alsoincludes as part of its bus controller units point-to-point (P-P)interfaces 2076 and 2078; similarly, second processor 2080 includes P-Pinterfaces 2086 and 2088. Processors 2070, 2080 may exchange informationvia a point-to-point (P-P) interface 2050 using P-P interface circuits2078, 2088. As shown in FIG. 20, IMCs 2072 and 2082 couple theprocessors to respective memories, namely a memory 2032 and a memory2034, which may be portions of main memory locally attached to therespective processors.

Processors 2070, 2080 may each exchange information with a chipset 2090via individual P-P interfaces 2052, 2054 using point to point interfacecircuits 2076, 2094, 2086, 2098. Chipset 2090 may optionally exchangeinformation with the coprocessor 2038 via a high-performance interface2092. In one embodiment, the coprocessor 2038 is a special-purposeprocessor, such as, for example, a high-throughput MIC processor, anetwork or communication processor, compression engine, graphicsprocessor, GPGPU, embedded processor, or the like.

A shared cache (not shown) may be included in either processor oroutside of both processors, yet connected with the processors via P-Pinterconnect, such that either or both processors' local cacheinformation may be stored in the shared cache if a processor is placedinto a low power mode.

Chipset 2090 may be coupled to a first bus 2016 via an interface 2096.In one embodiment, first bus 2016 may be a Peripheral ComponentInterconnect (PCI) bus, or a bus such as a PCI Express bus or anotherthird generation I/O interconnect bus, although the scope of the presentinvention is not so limited.

As shown in FIG. 20, various I/O devices 2014 may be coupled to firstbus 2016, along with a bus bridge 2018 which couples first bus 2016 to asecond bus 2020. In one embodiment, one or more additional processor(s)2015, such as coprocessors, high-throughput MIC processors, GPGPU's,accelerators (such as, e.g., graphics accelerators or digital signalprocessing (DSP) units), field programmable gate arrays, or any otherprocessor, are coupled to first bus 2016. In one embodiment, second bus2020 may be a low pin count (LPC) bus. Various devices may be coupled toa second bus 2020 including, for example, a keyboard and/or mouse 2022,communication devices 2027 and a storage unit 2028 such as a disk driveor other mass storage device which may include instructions/code anddata 2030, in one embodiment. Further, an audio I/O 2024 may be coupledto the second bus 2020. Note that other architectures are possible. Forexample, instead of the point-to-point architecture of FIG. 20, a systemmay implement a multi-drop bus or other such architecture.

Referring now to FIG. 21, shown is a block diagram of a second morespecific exemplary system 2100 in accordance with an embodiment of thepresent invention. Like elements in FIGS. 20 and 21 bear like referencenumerals, and certain aspects of FIG. 20 have been omitted from FIG. 21in order to avoid obscuring other aspects of FIG. 21.

FIG. 21 illustrates that the processors 2070, 2080 may includeintegrated memory and I/O control logic (“CL”) 2072 and 2082,respectively. Thus, the CL 2072, 2082 include integrated memorycontroller units and include I/O control logic. FIG. 21 illustrates thatnot only are the memories 2032, 2034 coupled to the CL 2072, 2082, butalso that I/O devices 2114 are also coupled to the control logic 2072,2082. Legacy I/O devices 2115 are coupled to the chipset 2090.

Referring now to FIG. 22, shown is a block diagram of a SoC 2200 inaccordance with an embodiment of the present invention. Similar elementsin FIG. 18 bear like reference numerals. Also, dashed lined boxes areoptional features on more advanced SoCs. In FIG. 22, an interconnectunit(s) 2202 is coupled to: an application processor 2210 which includesa set of one or more cores 1802A-N, which include cache units 1804A-N,and shared cache unit(s) 1806; a system agent unit 1810; a buscontroller unit(s) 1816; an integrated memory controller unit(s) 1814; aset or one or more coprocessors 2220 which may include integratedgraphics logic, an image processor, an audio processor, and a videoprocessor; an static random access memory (SRAM) unit 2230; a directmemory access (DMA) unit 2232; and a display unit 2240 for coupling toone or more external displays. In one embodiment, the coprocessor(s)2220 include a special-purpose processor, such as, for example, anetwork or communication processor, compression engine, GPGPU, ahigh-throughput MIC processor, embedded processor, or the like.

Embodiments of the mechanisms disclosed herein may be implemented inhardware, software, firmware, or a combination of such implementationapproaches. Embodiments of the invention may be implemented as computerprograms or program code executing on programmable systems comprising atleast one processor, a storage system (including volatile andnon-volatile memory and/or storage elements), at least one input device,and at least one output device.

Program code, such as code 2030 illustrated in FIG. 20, may be appliedto input instructions to perform the functions described herein andgenerate output information. The output information may be applied toone or more output devices, in known fashion. For purposes of thisapplication, a processing system includes any system that has aprocessor, such as, for example; a digital signal processor (DSP), amicrocontroller, an application specific integrated circuit (ASIC), or amicroprocessor.

The program code may be implemented in a high level procedural or objectoriented programming language to communicate with a processing system.The program code may also be implemented in assembly or machinelanguage, if desired. In fact, the mechanisms described herein are notlimited in scope to any particular programming language. In any case,the language may be a compiled or interpreted language.

One or more aspects of at least one embodiment may be implemented byrepresentative instructions stored on a machine-readable medium whichrepresents various logic within the processor, which when read by amachine causes the machine to fabricate logic to perform the techniquesdescribed herein. Such representations, known as “IP cores” may bestored on a tangible, machine readable medium and supplied to variouscustomers or manufacturing facilities to load into the fabricationmachines that actually make the logic or processor.

Such machine-readable storage media may include, without limitation,non-transitory, tangible arrangements of articles manufactured or formedby a machine or device, including storage media such as hard disks, anyother type of disk including floppy disks, optical disks, compact diskread-only memories (CD-ROMs), compact disk rewritable's (CD-RWs), andmagneto-optical disks, semiconductor devices such as read-only memories(ROMs), random access memories (RAMs) such as dynamic random accessmemories (DRAMs), static random access memories (SRAMs), erasableprogrammable read-only memories (EPROMs), flash memories, electricallyerasable programmable read-only memories (EEPROMs), phase change memory(PCM), magnetic or optical cards, or any other type of media suitablefor storing electronic instructions.

Accordingly, embodiments of the invention also include non-transitory,tangible machine-readable media containing instructions or containingdesign data, such as Hardware Description Language (HDL), which definesstructures, circuits, apparatuses, processors and/or system featuresdescribed herein. Such embodiments may also be referred to as programproducts.

Emulation (Including Binary Translation, Code Morphing, etc.)

In some cases, an instruction converter may be used to convert aninstruction from a source instruction set to a target instruction set.For example, the instruction converter may translate (e.g., using staticbinary translation, dynamic binary translation including dynamiccompilation), morph, emulate, or otherwise convert an instruction to oneor more other instructions to be processed by the core. The instructionconverter may be implemented in software, hardware, firmware, or acombination thereof. The instruction converter may be on processor, offprocessor, or part on and part off processor.

FIG. 23 is a block diagram contrasting the use of a software instructionconverter to convert binary instructions in a source instruction set tobinary instructions in a target instruction set according to embodimentsof the invention. In the illustrated embodiment, the instructionconverter is a software instruction converter, although alternativelythe instruction converter may be implemented in software, firmware,hardware, or various combinations thereof. FIG. 23 shows a program in ahigh level language 2302 may be compiled using an x86 compiler 2304 togenerate x86 binary code 2306 that may be natively executed by aprocessor with at least one x86 instruction set core 2316. The processorwith at least one x86 instruction set core 2316 represents any processorthat can perform substantially the same functions as an Intel® processorwith at least one x86 instruction set core by compatibly executing orotherwise processing (1) a substantial portion of the instruction set ofthe Intel® x86 instruction set core or (2) object code versions ofapplications or other software targeted to run on an Intel® processorwith at least one x86 instruction set core, in order to achievesubstantially the same result as an Intel® processor with at least onex86 instruction set core. The x86 compiler 2304 represents a compilerthat is operable to generate x86 binary code 2306 (e.g., object code)that can, with or without additional linkage processing, be executed onthe processor with at least one x86 instruction set core 2316.Similarly, FIG. 23 shows the program in the high level language 2302 maybe compiled using an alternative instruction set compiler 2308 togenerate alternative instruction set binary code 2310 that may benatively executed by a processor without at least one x86 instructionset core 2314 (e.g., a processor with cores that execute the MIPSinstruction set of MIPS Technologies of Sunnyvale, Calif. and/or thatexecute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.).The instruction converter 2312 is used to convert the x86 binary code2306 into code that may be natively executed by the processor without anx86 instruction set core 2314. This converted code is not likely to bethe same as the alternative instruction set binary code 2310 because aninstruction converter capable of this is difficult to make; however, theconverted code will accomplish the general operation and be made up ofinstructions from the alternative instruction set. Thus, the instructionconverter 2312 represents software, firmware, hardware, or a combinationthereof that, through emulation, simulation or any other process, allowsa processor or other electronic device that does not have an x86instruction set processor or core to execute the x86 binary code 2306.

EXAMPLES

Example 1 is a processor core. The processor core includes a decodecircuit to decode an instruction, where the instruction specifies anaddress to be monitored. The processor core further includes a monitorcircuit, where the monitor circuit includes a data structure to store aplurality of entries for addresses that are being monitored by themonitor circuit and a triggered queue, where the monitor circuit is toenqueue an address being monitored by the monitor circuit into thetriggered queue in response to a determination that a triggering eventfor the address being monitored by the monitor circuit occurred. Theprocessor core further includes an execution circuit to execute thedecoded instruction to add an entry for the specified address to bemonitored into the data structure and ensure, using a cache coherenceprotocol, that a coherency status of a cache line corresponding to thespecified address to be monitored is in a shared state.

Example 2 includes the substance of example 1. In this example, theexecution circuit is to return an indication that the specified addressto be monitored is already being monitored by the monitor circuit inresponse to a determination that the entry for the specified address tobe monitored exists in the data structure.

Example 3 includes the substance of example 1. In this example, theexecution circuit is to return an indication that the data structure isfull in response to a determination that there is no free entryavailable in the data structure.

Example 4 includes the substance of example 1. In this example, themonitor circuit is to free the entry for the specified address to bemonitored in response to the determination that the triggering event forthe specified address to be monitored occurred.

Example 5 includes the substance of example 1. In this example, themonitor circuit includes an overflow indicator and the monitor circuitis to set the overflow indicator in response to a determination that thetriggered queue has overflowed.

Example 6 includes the substance of example 1. In this example, themonitor circuit is to determine that a triggering event for thespecified address being monitored occurred based on a determination thatthat the coherency status of the cache line corresponding to thespecified address to be monitored has changed.

Example 7 includes the substance of example 1. In this example, theentry for the specified address to be monitored includes an indicationof a logical address corresponding to the specified address to bemonitored and an indication of a physical address corresponding to thespecified address to be monitored.

Example 8 is a method performed by a processor core. The method includesdecoding an instruction, where the instruction specifies an address tobe monitored and executing the decoded instruction to add an entry forthe specified address to be monitored into a data structure of a monitorcircuit and ensure, using a cache coherence protocol, that a coherencystatus of a cache line corresponding to the specified address to bemonitored is in a shared state, where the monitor circuit is to enqueuethe specified address to be monitored into a triggered queue of themonitor circuit in response to a determination that a triggering eventfor the specified address to be monitored occurred.

Example 9 includes the substance of example 8. In this example, theexecution is to return an indication that the specified address to bemonitored is already being monitored by the monitor circuit in responseto a determination that the entry for the specified address to bemonitored exists in the data structure.

Example 10 includes the substance of example 8. In this example, theexecution is to return an indication that the data structure is full inresponse to a determination that there is no free entry available in thedata structure.

Example 11 includes the substance of example 8. In this example, themonitor circuit is to free the entry for the specified address to bemonitored in response to the determination that the triggering event forthe specified address to be monitored occurred.

Example 12 includes the substance of example 8. In this example, themonitor circuit includes an overflow indicator, and the monitor circuitis to set the overflow indicator in response to a determination that thetriggered queue has overflowed.

Example 13 includes the substance of example 8. In this example, themonitor circuit is to determine that a triggering event for thespecified address being monitored occurred based on a determination thatthat the coherency status of the cache line corresponding to thespecified address to be monitored has changed.

Example 14 includes the substance of example 8. In this example, theentry for the specified address to be monitored includes an indicationof a logical address corresponding to the specified address to bemonitored and an indication of a physical address corresponding to thespecified address to be monitored.

Example 15 is a non-transitory computer-readable storage medium havingstored therein instructions. The instructions, when executed by aprocessor core, cause the processor core to decode the instruction,where the instruction specifies an address to be monitored and executethe decoded instruction to add an entry for the specified address to bemonitored into a data structure of a monitor circuit and ensure, using acache coherence protocol, that a coherency status of a cache linecorresponding to the specified address to be monitored is in a sharedstate, where the monitor circuit is to enqueue the specified address tobe monitored into a triggered queue of the monitor circuit in responseto a determination that a triggering event for the specified address tobe monitored occurred.

Example 16 includes the substance of example 15. In this example, theexecution is to return an indication that the specified address to bemonitored is already being monitored by the monitor circuit in responseto a determination that the entry for the specified address to bemonitored exists in the data structure.

Example 17 includes the substance of example 15. In this example, theexecution is to return an indication that the data structure is full inresponse to a determination that there is no free entry available in thedata structure.

Example 18 includes the substance of example 15. In this example, themonitor circuit is to free the entry for the specified address to bemonitored in response to the determination that the triggering event forthe specified address to be monitored occurred.

Example 19 includes the substance of example 15. In this example, themonitor circuit includes an overflow indicator, and the monitor circuitis to set the overflow indicator in response to a determination that thetriggered queue has overflowed.

Example 20 includes the substance of example 16. In this example, themonitor circuit is to determine that a triggering event for thespecified address being monitored occurred based on a determination thatthat the coherency status of the cache line corresponding to thespecified address to be monitored has changed.

Example 21 includes the substance of example 15. In this example, theentry for the specified address to be monitored includes an indicationof a logical address corresponding to the specified address to bemonitored and an indication of a physical address corresponding to thespecified address to be monitored.

Example 22 is a system. The system includes a decode circuit to decodean instruction, where the instruction specifies an address to bemonitored. The system further includes a monitor circuit, where themonitor circuit includes a data structure to store a plurality ofentries for addresses that are being monitored by the monitor circuitand a triggered queue, where the monitor circuit is to enqueue anaddress being monitored by the monitor circuit into the triggered queuein response to a determination that a triggering event for the addressbeing monitored by the monitor circuit occurred. The system furtherincludes an execution circuit to execute the decoded instruction to addan entry for the specified address to be monitored into the datastructure and ensure, using a cache coherence protocol, that a coherencystatus of a cache line corresponding to the specified address to bemonitored is in a shared state.

Example 23 includes the substance of example 22. In this example, theexecution circuit is to return an indication that the specified addressto be monitored is already being monitored by the monitor circuit inresponse to a determination that the entry for the specified address tobe monitored exists in the data structure.

Example 24 includes the substance of example 22. In this example, theexecution circuit is to return an indication that the data structure isfull in response to a determination that there is no free entryavailable in the data structure.

Example 25 includes the substance of example 22. In this example, themonitor circuit is to free the entry for the specified address to bemonitored in response to the determination that the triggering event forthe specified address to be monitored occurred.

Example 26 includes the substance of example 22. In this example, themonitor circuit includes an overflow indicator and the monitor circuitis to set the overflow indicator in response to a determination that thetriggered queue has overflowed.

Example 27 includes the substance of example 22. In this example, themonitor circuit is to determine that a triggering event for thespecified address being monitored occurred based on a determination thatthat the coherency status of the cache line corresponding to thespecified address to be monitored has changed.

Example 28 is a processor core. The processor core includes a decodingmeans to decode an instruction, where the instruction specifies anaddress to be monitored. The processor core further includes amonitoring means, where the monitoring means includes a data structureto store a plurality of entries for addresses that are being monitoredby the monitoring means and a triggered queue, where the monitoringmeans is to enqueue an address being monitored by the monitoring meansinto the triggered queue in response to a determination that atriggering event for the address being monitored by the monitoring meansoccurred. The processor core further includes an executing means toexecute the decoded instruction to add an entry for the specifiedaddress to be monitored into the data structure and ensure, using acache coherence protocol, that a coherency status of a cache linecorresponding to the specified address to be monitored is in a sharedstate.

Example 29 includes the substance of example 28. In this example, theentry for the specified address to be monitored includes an indicationof a logical address corresponding to the specified address to bemonitored and an indication of a physical address corresponding to thespecified address to be monitored.

Example 30 is a processor core. The processor core includes a decodecircuit to decode an instruction. The processor core further includes amonitor circuit, where the monitor circuit includes a data structure tostore a plurality of entries for addresses that are being monitored bythe monitor circuit and a triggered queue to store a plurality ofaddresses for which a triggering event occurred. The processor corefurther includes an execution circuit to execute the decoded instructionto dequeue an address from the triggered queue and return the dequeuedaddress in response to a determination that the triggered queue is notempty.

Example 31 includes the substance of example 30. In this example, theexecution circuit is to cause the processor core to enter an optimizedstate in response to a determination that the triggered queue is emptyand to cause the processor core to exit the optimized state in responseto a determination that a triggering event for an address beingmonitored by the monitor circuit occurred.

Example 32 includes the substance of example 30. In this example, theexecution circuit is to return an indication that a triggering event foran address being monitored by the monitor circuit has not occurred inresponse to a determination that the triggered queue is empty.

Example 33 includes the substance of example 30. In this example, themonitor circuit includes an overflow indicator and the execution circuitis to return an indication that the triggered queue has overflowed inresponse to a determination that the overflow indicator is set and alsoreset the overflow indicator.

Example 34 includes the substance of example 30. In this example, theexecution circuit is to return an indication that no addresses are beingmonitored by the monitor circuit in response to a determination that thetriggered queue is empty and the data structure is empty.

Example 35 includes the substance of example 34. In this example, theexecution circuit is to determine that the data structure is empty basedon a determination that a content of the data structure indicates thatno addresses are being monitored by the monitor circuit.

Example 36 includes the substance of example 30. In this example, theexecution circuit is to store the dequeued address in a destinationregister.

Example 37 is a method performed by a processor core. The methodincludes decoding an instruction and executing the decoded instructionto dequeue an address from a triggered queue of a monitor circuit andreturn the dequeued address in response to a determination that thetriggered queue is not empty, where the monitor circuit includes a datastructure to store a plurality of entries for addresses that are beingmonitored by the monitor circuit and where the triggered queue to storea plurality of addresses for which a triggering event occurred.

Example 38 includes the substance of example 37. In this example, theexecution is to cause the processor core to enter an optimized state inresponse to a determination that the triggered queue is empty and tocause the processor core to exit the optimized state in response to adetermination that a triggering event for an address being monitored bythe monitor circuit occurred.

Example 39 includes the substance of example 37. In this example, theexecution is to return an indication that a triggering event for anaddress being monitored by the monitor circuit has not occurred inresponse to a determination that the triggered queue is empty.

Example 40 includes the substance of example 37. In this example, themonitor circuit includes an overflow indicator and the execution is toreturn an indication that the triggered queue has overflowed in responseto a determination that the overflow indicator is set and reset theoverflow indicator.

Example 41 includes the substance of example 37. In this example, theexecution is to return an indication that no addresses are beingmonitored by the monitor circuit in response to a determination that thetriggered queue is empty and the data structure is empty.

Example 42 includes the substance of example 41. In this example, theexecution is to determine that the data structure is empty based on adetermination that a content of the data structure indicates that noaddresses are being monitored by the monitor circuit.

Example 43 includes the substance of example 37. In this example, theexecution is to store the dequeued address in a destination register.

Example 44 is a non-transitory computer-readable storage medium havingstored therein instructions. The instructions, when executed by aprocessor core, cause the processor core to decode the instruction andexecute the decoded instruction to dequeue an address from a triggeredqueue of a monitor circuit and return the dequeued address in responseto a determination that the triggered queue is not empty, where themonitor circuit includes a data structure to store a plurality ofentries for addresses that are being monitored by the monitor circuitand where the triggered queue to store a plurality of addresses forwhich a triggering event occurred.

Example 45 includes the substance of example 44. In this example, theexecution is to cause the processor core to enter an optimized state inresponse to a determination that the triggered queue is empty and tocause the processor core to exit the optimized state in response to adetermination that a triggering event for an address being monitored bythe monitor circuit occurred.

Example 46 includes the substance of example 44. In this example, theexecution is to return an indication that a triggering event for anaddress being monitored by the monitor circuit has not occurred inresponse to a determination that the triggered queue is empty.

Example 47 includes the substance of example 44. In this example, themonitor circuit includes an overflow indicator and the execution is toreturn an indication that the triggered queue has overflowed in responseto a determination that the overflow indicator is set and reset theoverflow indicator.

Example 48 includes the substance of example 44. In this example, theexecution is to return an indication that no addresses are beingmonitored by the monitor circuit in response to a determination that thetriggered queue is empty and the data structure is empty.

Example 49 includes the substance of example 48. In this example, theexecution is to determine that the data structure is empty based on adetermination that a content of the data structure indicates that noaddresses are being monitored by the monitor circuit.

Example 50 includes the substance of example 44. In this example, theexecution is to store the dequeued address in a destination register.

Example 51 is a system. The system includes a decode circuit to decodean instruction. The system further includes a monitor circuit, where themonitor circuit includes a data structure to store a plurality ofentries for addresses that are being monitored by the monitor circuitand a triggered queue to store a plurality of addresses for which atriggering event occurred. The system further includes an executioncircuit to execute the decoded instruction to dequeue an address fromthe triggered queue and return the dequeued address in response to adetermination that the triggered queue is not empty.

Example 52 includes the substance of example 51. In this example, theexecution circuit is to cause a processor core to enter an optimizedstate in response to a determination that the triggered queue is emptyand to cause the processor core to exit the optimized state in responseto a determination that a triggering event for an address beingmonitored by the monitor circuit occurred.

Example 53 includes the substance of example 51. In this example, theexecution circuit is to return an indication that a triggering event foran address being monitored by the monitor circuit has not occurred inresponse to a determination that the triggered queue is empty.

Example 54 includes the substance of example 51. In this example, themonitor circuit includes an overflow indicator and the execution circuitis to return an indication that the triggered queue has overflowed inresponse to a determination that the overflow indicator is set and alsoreset the overflow indicator.

Example 55 includes the substance of example 51. In this example, theexecution circuit is to return an indication that no addresses are beingmonitored by the monitor circuit in response to a determination that thetriggered queue is empty and the data structure is empty.

Example 56 includes the substance of example 55. In this example, theexecution circuit is to determine that the data structure is empty basedon a determination that a content of the data structure indicates thatno addresses are being monitored by the monitor circuit.

Example 57 is a processor core. The processor core includes a decodingmeans to decode an instruction. The processor core further includes amonitoring means, where the monitoring means includes a data structureto store a plurality of entries for addresses that are being monitoredby the monitoring means and a triggered queue to store a plurality ofaddresses for which a triggering event occurred. The processor corefurther includes an executing means to execute the decoded instructionto dequeue an address from the triggered queue and return the dequeuedaddress in response to a determination that the triggered queue is notempty.

Example 58 includes the substance of example 57. In this example, theexecuting means is to store the dequeued address in a destinationregister.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described, can be practiced with modificationand alteration within the spirit and scope of the appended claims. Thedescription is thus to be regarded as illustrative instead of limiting.

1. A processor core comprising: a decode circuit to decode aninstruction; a monitor circuit, wherein the monitor circuit includes adata structure to store a plurality of entries for addresses that arebeing monitored by the monitor circuit and a triggered queue to store aplurality of addresses for which a triggering event occurred; and anexecution circuit to execute the decoded instruction to dequeue anaddress from the triggered queue and return the dequeued address inresponse to a determination that the triggered queue is not empty. 2.The processor core of claim 1, wherein the execution circuit is to causethe processor core to enter an optimized state in response to adetermination that the triggered queue is empty and is to cause theprocessor core to exit the optimized state in response to adetermination that a triggering event for an address being monitored bythe monitor circuit occurred.
 3. The processor core of claim 1, whereinthe execution circuit is to return an indication that a triggering eventfor an address being monitored by the monitor circuit has not occurredin response to a determination that the triggered queue is empty.
 4. Theprocessor core of claim 1, wherein the monitor circuit includes anoverflow indicator, and wherein the execution circuit is to return anindication that the triggered queue has overflowed in response to adetermination that the overflow indicator is set and is to reset theoverflow indicator.
 5. The processor core of claim 1, wherein theexecution circuit is to return an indication that no addresses are beingmonitored by the monitor circuit in response to a determination that thetriggered queue is empty and the data structure is empty.
 6. Theprocessor core of claim 5, wherein the execution circuit is to determinethat the data structure is empty based on a determination that a contentof the data structure indicates that no addresses are being monitored bythe monitor circuit.
 7. The processor core of claim 1, wherein theexecution circuit is to store the dequeued address in a destinationregister.
 8. A method performed by a processor core, comprising:decoding an instruction; and executing the decoded instruction todequeue an address from a triggered queue of a monitor circuit andreturn the dequeued address in response to a determination that thetriggered queue is not empty, wherein the monitor circuit includes adata structure to store a plurality of entries for addresses that arebeing monitored by the monitor circuit and wherein the triggered queueis to store a plurality of addresses for which a triggering eventoccurred.
 9. The method of claim 8, wherein the execution of the decodedinstruction is to cause the processor core to enter an optimized statein response to a determination that the triggered queue is empty, andcause the processor core to exit the optimized state in response to adetermination that a triggering event for an address being monitored bythe monitor circuit occurred.
 10. The method of claim 8, wherein theexecution of the decoded instruction is to return an indication that atriggering event for an address being monitored by the monitor circuithas not occurred in response to a determination that the triggered queueis empty.
 11. The method of claim 8, wherein the monitor circuitincludes an overflow indicator, and wherein the execution of the decodedinstruction is to return an indication that the triggered queue hasoverflowed in response to a determination that the overflow indicator isset and is to reset the overflow indicator.
 12. The method of claim 8,wherein the execution of the decoded instruction is to return anindication that no addresses are being monitored by the monitor circuitin response to a determination that the triggered queue is empty and thedata structure is empty.
 13. The method of claim 12, wherein thedetermination that the data structure is empty based on a determinationthat a content of the data structure indicates that no addresses arebeing monitored by the monitor circuit.
 14. The method of claim 8,wherein the execution of the decoded instruction is to store thedequeued address in a destination register.
 15. A non-transitorycomputer-readable storage medium having stored therein instructions,which when executed by a processor core, causes the processor core to:decode an instruction; and execute the decoded instruction to dequeue anaddress from a triggered queue of a monitor circuit and return thedequeued address in response to a determination that the triggered queueis not empty, wherein the monitor circuit includes a data structure tostore a plurality of entries for addresses that are being monitored bythe monitor circuit and wherein the triggered queue is to store aplurality of addresses for which a triggering event occurred.
 16. Thenon-transitory computer-readable storage medium of claim 15, wherein theexecution of the decoded instruction is to cause the processor core toenter an optimized state in response to a determination that thetriggered queue is empty, and cause the processor core to exit theoptimized state in response to a determination that a triggering eventfor an address being monitored by the monitor circuit occurred.
 17. Thenon-transitory computer-readable storage medium of claim 15, wherein theexecution of the decoded instruction is to return an indication that atriggering event for an address being monitored by the monitor circuithas not occurred in response to a determination that the triggered queueis empty.
 18. The non-transitory computer-readable storage medium ofclaim 15, wherein the monitor circuit includes an overflow indicator,and wherein the execution of the decoded instruction is to return anindication that the triggered queue has overflowed in response to adetermination that the overflow indicator is set and is to reset theoverflow indicator.
 19. The non-transitory computer-readable storagemedium of claim 15, wherein the execution of the decoded instruction isto return an indication that no addresses are being monitored by themonitor circuit in response to a determination that the triggered queueis empty and the data structure is empty.
 20. The non-transitorycomputer-readable storage medium of claim 19, wherein the determinationthat the data structure is empty is based on a determination that acontent of the data structure indicates that no addresses are beingmonitored by the monitor circuit.
 21. The non-transitorycomputer-readable storage medium of claim 15, wherein the execution ofthe decoded instruction is to store the dequeued address in adestination register.